Do you think it is because of this impracticality or for some other reason?
I also have similar question, since this occurrence also happen to all kinds of spammer (SEO spam, AI spam, advertising spam and more). Based on my experience, it could go as fast as getting nuked within minutes and no action even after i reported more than half of all spam post they created.
Your case, of course, is a violation that has been proven repeatedly, but the fact that the account already has a negative tag tells us that it will exist on the forum as long as its signature exists. All other managers will ignore this account, which will make it unnecessary.
But FWIW, they still have benefit of high ranked account to perform spam with much less limitation compared with new account. IMO moderator should consider to take action against high ranked account, due to that reason.