Why does Disk Utility pkg info show APPL?

All I can tell you is that it's normal, for Disk Utility.

All macOS apps have a PkgInfo file but its presence is for the benefit of legacy systems that used type and creator data. Recent macOS versions have no use for it, so its contents are ignored as irrelevant.

APPL actually stood for "application" which described the type of file it was. The question marks were present when its creator was unknown.

Where, exactly, are you seeing this?

Disk Utility is a legit Apple app, so there's little to worry about in that regard.