It seems you are mixing the concepts of voting systems and candidate selection. FPP nor FPTP should not sound scary. As a voting systems, FPP works well enough more often than many want to admit. The name just describes it in more detail: First Preference Plurality.

Every voting system is as bottom-up or top-down as the candidate selection process. The voting system itself doesn't really affect whether it is top down or bottom up. Requiring approval/voting from the current rulers would be top-down. Only requiring ten signatures on a community petition is more bottom up.

The voting systems don't care about the candidate selection process. Some require precordination for a "party", but that could also be a party of 1. A party of 1 might not be able to get as much representation as one with more people: but that's also the case for every voting system that selects the same number of candidates.

Voting systems don't even need to be used for representation systems. If a group of friends are voting on where to eat, one problem might be selecting the places to vote on, but that's before the vote. With the vote, FPP might have 70% prefer pizza over Indian food, but the Indian food vote might still win because the pizza voters had another first choice. Having more candidates often leads to minority rule/choice, and that's not very good for food choice nor community representation.

He seems to think like a mathematician or philosopher and enjoyed considering each of those items separately, in isolation from one another - plus as a YouTuber, he needs to release moar content, moar often, so multiple videos helps him maintain his existence that way as opposed to a single, larger video, especially on a complex topic that since it is >1 minute long, the vast majority of people are not going to watch anyway.:-P

But anyway, if he's already mathematically proved certain things about e.g. ranked-choice, and how it differs from whatever else, then why should he bother going further into the weeds, that the vast majority of people don't care the tiniest bit about? After all, a look at basically every election ever, especially recently, reveals that the common people know next to nothing about how the system works. e.g. people voting against Hillary Clinton in 2016, either by voting 3rd party, or switching to the "Never Hillary" movement to actively vote for Trump, but then being shocked - shocked I tell you! SHOOKETH! - when he won. So if we can't figure out that 1+1=2, then differential calculus, much less simple algebra, is going to be beyond us (collectively) as well.

So, I took it as not that he refused to consider those other possibilities, just that he was focusing his description to explain one thing in isolation of other concepts, as much as possible at least. e.g. regardless of whether he should have been talking about (or naming it as) FPTP, that's what he was aiming to do, so that's what he did.

About the Rules for Rulers I think similarly as above but also: the "rulers" there aren't necessarily the ones in charge, as is true for the monarchies & totalitarian regimes, but rather the "voters" who put those people in charge. In that formulation, why should the non-voters (e.g. literal children, people who are mentally disabled, etc.) have power over & above that of the voters, i.e. the responsible "rulers"?

Although that is exactly what always ends up happening... eventually, in any such system. Imagine a person who votes, individually, but then also is responsible for gerrymandering a district of lets say a million people. So they should have had power equal to 1/1000000, though instead they overturned the decisions of those million people and single-handedly altered the election, FAR in excess of their individual voting power. They cannot overturn the collective weight of a full million voters all speaking with a single unified voice... but they could make a vote for e.g. 1/10th vs. 9/10ths end up with the former rather than the latter being in charge, which is pretty damn powerful (it doesn't have to be "perfect", it just has to work - possibly in conjunction with other things like removing certain classes of people as voters). So here, irl rather than in pure theory in isolation of irl considerations, "rulers" end up NOT being the voters, but rather those in charge b/c they are willing to cheat the system, to keep themselves in charge or at least others exactly like them, using non-voting schemes. i.e. it is the True Rulers(TM) who are "in charge" rather than the voting ones, who were put into place by non-voting systems, so the entire system gets turned upon its head and does if not 100% then still effectively the opposite of what it was originally intended to - that is, it ignores/overturns votes rather than uses them to determine the outcomes of elections.

So if we, the aspiring rulers i.e. voters, wish to actually rule, then we need to know what we are up against. And if others cheat... well then that does not mean that we have to as well, but we should at least be aware that that is what is going on!?! To some degree at least, even if not 100%, hence it is "biased" and "unfair" and "rigged". That is what I took from those videos, collectively.