There's an anti-footgun heuristic that asks "are you sure", basically, if the file about to be tracked is >=1mb, saved a lot of asses a lot of times.

But also, if it is such a showstopper, you can disable auto-amend of _new_ files with snapshot.auto-track=none() config (or even something funky like src/*) - and recently jj status finally started showing untracked files too, it's very usable