I think it's a false dichotomy if you're thinking of finding the root cause instead of speculative requests.

You can do none, one of them, or both. You may have team skills to tackle none, one, or both. You may or may not control / have access to one of the sides. You may have a timeline for solving this problem where you decide which task is faster to finish. Finally, you may have a recurring problem which makes you lose a specific amount of money every time and a speculative request stops that now, while putting people on a performance debugging mission may only potentially have a positive return in the future.

Sure, it's a technical debt. It's not illegal - you just need a really good reason to commit to it.