Nobody is arguing that usong a subset of tests won't catch all bugs. They are stating that having X% code coverage does not imply that you will be able to cat

Nobody is arguing that usong a subset of tests won't catch all bugs. They are stating that having X% code coverage does not imply that you will be able to catch X% of bugs (at least, of the trivial type they introduced here) so you shouldn't use code coverage as a proxy for how good your test suite is. This may be obvious to you, but I've definitely seen teams fall into the trap of using code coverage as a primary measure of how good testing is.