Thanks for responding, Christiaan.
<Insert sad trombone sound>
I have some vague recollection of a cross-version workaround in the 2019-2020 versions where I was the one who was behind a version, but I haven't had a collaborator in a while...
I love the Project Sharing features in VW. I've had excellent experiences with it at my previous company. I am running 2021, and I have a client who is still in 2020. If they share a project with me, what issues should I expect to face?