Blue
Ravenous Bugblatter Beast of Traal
Which rules are you referring to? Players don't get to decide they're making a Wisdom (Insight) check or any other kind of ability check. They might succeed or fail outright with no roll. All they get to do is describe a task they want to perform.
When talking about consistency in applying the rules that's for the DM, not the players.
You can call it a "house rule." It doesn't bother me. But it's not really. I'm still effectively deciding the result as DM. I'm just giving the players input. I'm not required to use mechanics to resolve a situation as DM. The rules serve me, not the other way around.
You are withholding information that you would have given the character if the speaker was an NPC. By your own words. You're pushing off the answer to others because you don't want to get involved. By your own words. That's not a result, it's a lack of result.
If you were in a university taking a test, they wouldn't give you credit for leaving the box blank. Nor if you wrote in the box "I decline to answer this but I'm sure between the professor and the teaching assistant they can come up with the right answer."