In gen 2 they split special into satk and sdef. Gyarados has 60 satk and 125 atk. Hyper beam being a normal move uses atk in gens 1-3. Hydro pump just gets worse. I doubt the way they changed stat calculations makes up for 65 attack power. Looking at this in Pokemon showdown I think there is something going on with these damage calcs. My guess is damage has a cap somewhere and these moves are hitting it before weakness/resistance multipliers are applied.

[–] [email protected] 1 points 1 year ago

Just in case anyone is curious it seems base damage in the formula is capped at 999 before modifiers. Later all damage is lowered to the defenders max hp if the damage is higher. Pokemon showdown seems to do the former but not the latter.