I would suspect no one wants to invest the legal team or time to be the "trailblazer" court case to find out whether your theory or the common interpretation is correct. The "just ban AGPL" stance is by far the safer route since it's not like there are no sane replacements for AGPL stuff
IANAL, and thus far my life is worse for any interaction with the legal system
It totally is safer, and I tend to agree with it in a business context. But the license itself doesn't seem to indicate that any kind of "RPC" is thus encumbered.
When MongoDB was under the AGPL, your application wasn't under the AGPL if you connected to it and asked it to do queries.
IANAL, and thus far my life is worse for any interaction with the legal system