Bro-science dictates that muscles peak at 35, so that would agree with you being stronger than 20 year olds (but not weaker that 50s).
Normally no, a 30 year old is supoosed to be stronger than a 50 year old. A 50 year old just has better skills and experience how to use his strength to compensate ..
Imagine a person that started serious strength conditioning at 40. He will be much stronger at 50 than average 18 yo football player if he „follows the program” ;) yes, it does accumulate a lot over time.
Average 50 year old is declined to about the same level as an average 18 year old so… this statement is probably accurate but uninteresting.
i think there is some truth to it. in my family men start out as quite slim during early adulthood and become more and more sturdy with age. arm width increasing significantly etc.