In tipical GNOME fashion, they have decided to replace this largely working piece of software with on with one that places solidly at the bottom of the article's list (ptyxis).
If you run:
GSK_RENDERER=cairo ptyxis -s
You can verify that with 69,985 here RES and 52,428 of that SHR. With 5 tabs open it jumped to 71,208 here. Presumably for the encrypted scrollback pre-allocations.
You still may not choose to use it, but it should stay relatively similar the more tabs you open.
Also, it's not a core GNOME app. It's just an app I wrote for me that the distros seem to have liked for its design/platform integration.
And I didn't really miss any features to be honest, it has the basic that you expect (things like tabs). It is less customizable than other options, but the defaults were good enough for me.