Worth pointing out that not all in-app browsers are created equal, however. A huge number of apps, probably the majority, on iOS use SFSafariViewController for theirs, which is basically an isolated Safari tab that runs out of process and app developers have no access to. Furthermore, SFSafariViewController instances are unique per-app, each with their own separate set of cookies so apps can’t trick you into visiting a link to gain access to full Safari’s cookies.

IIRC Android has something similar that opens an isolated Chrome tab within apps but I have no idea how common usage of that is in Android apps.