The issue is not forwarding the email. The issue is people sending email to the Google address in the first place. As someone who just set up email on his own domain, I'm starting to wish I could search every database and contacts list for my old Google address and replace it with the new one which is actually mine.
That seems like an invitation for long-term pain if Google changes their policies, requiring someone to log in every X months or have their gmail account locked, for example, or some AI enforcement tool locks the account for inscrutable reasons.
I'm locked out of my Gmail and it still forwards to the recovery email address, but I can't get in to change the settings. They also won't allow me to download all my data, as required by statute, because I can't log in.
I've got some active GMail forwarding addresses that I haven't logged into for 10+ years. I don't think they could change how that worked now even if they wanted to.