[faho]

Bash also turns off the bracketed paste, because it can't know if the command it is about to launch supports it. So that command would have to re-enable it itself. Something like emacs or vim might do so (or another bash, you can nest shells).

And yes, then bash starts ls, which is an external program. It might be /usr/bin/ls.

And then ls quits, and bash re-enables bracketed paste because the command might have not enabled it or enabled it and disabled it before quitting. So you get this weird bracketed paste sandwich.