That's my understanding as well, but I also understand that the email will pass DMARC if either SPF or DKIM passes, and DKIM will still pass on forwarded email.
Yeah, with forwarding, I am seeing DKIM still passes but SPF fails.
We are seeing all the unix forwarders setup a decade+ ago are dead in the water now (have to be replaced with mailing list software)
This explains why I have been unable to get my 2FA from Adobe.