Hamilton and Gasly is pretty clear cut. Gasly locked up and Hamilton couldn't respond in time which is why Hamilton hit Gasly, that's a pretty clear racing incident. Norris and Perez isn't that clear cut.

I can absolutely understanding arguing that it was just a racing incident because Perez didn't expect Norris to turn in and Norris didn't expect Perez to run wide. But at the same time there's an argument to be made that Perez could've turned into the apex but decided to go wide (and watching it back it does seem like he doesn't really commit to the apex which makes him go wide).

The stewards seemed to have gone for the latter explanation and given him a penalty, which seems like a consistent ruling considering Max got the same penalty for a similar situation in Las Vegas (and there Max had a bigger case for it being a racing incident).

Gasly locked up, if he hadn't Lewis wouldn't have hit him. As Gasly lost control of his car first it's a racing incident. If Gasly hadn't first locked up Lewis would be looking at a penalty.