I liked Ronnie a lot, but Iran Contra will always be a stain on his record, same with JFK and the Bay of Pigs. His reputation and standing have taken a big hit and owning it does acknowledge that.
It has also certainly hurt him significantly with the electorate. His numbers are now at Orange levels.
He would, of course have these whether he “owned it” or not. But it’s a least an acknowledgement that he bears the consequences of this fiasco.