> A horrible design flaw that made ~50% of users take 20 seconds to get a query answered was buried, because a manager involved was the one who wrote the code.

Maybe not when it is as much as 20 seconds, but an old manager of mine would save fixing something like that for a “quick win” at some later time! He would even have artificial delays put in, enough to be noticeable and perhaps reported but not enough to be massively inconvenient, so we could take them out during the UAT process - it didn't change what the client finally got, but it seemed to work especially if they thought they'd forced us to spend time on performance issues (those talking to us at the client side could report this back up their chain as a win).

There is a term for this but I can't remember what it's called.

Effectively you put in on purpose bugs for an inspector to find so they don't dig too deep for difficult to solve problems.