The point of this is if you have an existing program which does already has exploitable use-after-free bug, then Alpine Linux's libc makes it easier to convert

The point of this is if you have an existing program which does already has exploitable use-after-free bug, then Alpine Linux's libc makes it easier to convert that exploit into full code execution. This specifically talks about lack of hardening - there is no new way to attack a program which had no use-after-free vulnerability to begin with.