The reason (it seems) they stick to one timezone, are comments /updates can be added to status page incidents. It can be conflicting to talk about event times in a comment, and the post has different times. Here's an example from slack, where it's mixed, comments in PDT and posts in the local timezone. https://status.slack.com/2019-06-28. I think it's a setting in statuspage, but it's tough decide which is best. I definitely wouldn't prefer looking at it in UTC.

This is just incorrect. I mean, Date.toISOString() will do that. Plus, it's very likely that this is just what's written in the post by the author and may have nothing to do with JavaScript. Or it could be JS that converts times to local time (I'm in PDT, so I can't tell), which is what a lot of sites do.

During the handling of an incident, the last thing you want to think twice about is timezones, so it is understandable for Discord who started in PT to just use PT universally. (Eventually, or perhaps already, it will just become a weird quirk of history.)