That’s just the app itself, not the actual browser engine - under the hood it’s still WebKit (what Safari uses) and not Chrome or any other browser engine: https://en.m.wikipedia.org/wiki/WebKit#Use
iOS doesn’t allow anything other than WebKit webviews described above. Android does support others, but that’s a different story.
That's not what the question/context was -- it was specifically talking about which app (e.g. Safari, Chrome, Firefox, whatever) is used to open links from apps.
No clue why I was downvoted for saying that, which was a perfectly valid answer in that context.
Yes they can, starting with iOS 14: https://support.apple.com/en-us/HT211336