iframe height & overflow?

obviously i can write some custom css for this, but any ideas why the iframe for the custom page in the dashboard is so small by default?

see here: https://www.dropbox.com/scl/fi/wjxyo5jhocvgdsma2ivmd/Screenshot-2026-03-03-at-1.35.09-AM.png?rlkey=ygwqc5y8yhh9ryamy1bbf41gp&dl=0