Being at the gate 30 minutes is for intl, its actually 15 min for domestic.
That is not a new change and was around with the original limits before this recent change (looking at web.archive.org).

And honestly 15 minutes before departure is starting to cut it close to me, especially since the doors can close early and you might be subject to offloading. For international given that there may be additional time needed to board depending on the point of departure, it makes sense that they say to be there at the 30 minute mark prior to departure.

Now I don't think that especially for intl that they'll offload you at the 30 minute mark, especially since people will likely still be boarding at that point, so you probably could push it, but you're going to start to play with fire if you really want that extra 15 minutes that you think you had (but you actually never did in the first place).