bb raise

Heard some advice today that was new to me, but makes sense. If the bb
raises a previously unraised pot, preflop, he is most likely holding a pocket pair. Any other holding would want to see a "free" flop.
Following the same logic, it's worth calling and betting at him/her on an A high flop.
Is this common knowledge? Is it worth the risk?

mmmm i dont think so.

Theres no such thing as set rules and standards like that.

id imagine most players would raise the BB with AK or AQ too...

Besides, in an unraised pot sometimes a BB might raise with any two cards and try to steal the pot.