Most managers I've worked with haven't been shy about saying this. It's usually followed by "...but try asking <x>" or "Let me find out and get back to you".
To be honest, if anyone, in any role, never says "I don't know", I begin to question their abilities.
I worked for 5 years at an American company in Australia and I heard this multiple times per day from my US colleagues - my conclusion after heard it said to the most basic questions was that it’s mostly a filler phrase used to buy time while the respondent thinks up an answer.
Not super relevant but I’ve noticed recently that when I ask someone a question, they start their answer with the word “absolutely” even though the question was not a yes or no question.
Is this a time-filler like “that’s a great question” for extreme people pleasers? Or just an agreeability signal? To me it makes the answerer seem overeager to share. It could just be regional culture.
Depends heavily on how it's said. If it's flat with no derivation from the previous sentences intonation, it is probably filler. If it intentionally stands out, it is probably not.
Personally, I use the phrase often as a Senior IC in a way that makes it clear it t is not filler. I also use phrases such as, "Hell if I know, let's google it and find out together."
Yeah, if anything, managers bluff and pretend to know significantly more often then engineers. And those who don't, gets removed or are seen as less capable by those over them.
One of the signs of a healthy culture is that people are not afraid to acknowledge knowledge gaps.