I think it’s hilarious that the primes were all treated as long gone legends, lost to time, and then there’s the guard who knew all of them (probably personally) and just never mention that fact.
Could you imagine Megatron going all “Tell me about Megatronus” and he’s expecting kickass war stories or battle techniques and all Starscream or anyone can think of is that time Megatronus hit his head on a doorframe so hard he passed out