Seedvault is not a good backup solution. The devs who promote it don't have a lot of credibility. It basically doesn't work half the time and they know it, but pretend it's great to pad their resumes.
Even the core LineageOS and Graphine devs spend time disparaging it on reddit and twitter with comments like "It's not a very good app." and "Unfortunately Seedvault is still unreliable." Those are direct quotes.
I think it was back on LineageOS 16 that it was actually broken for the entire release. It wasn't even possible to do a basic backup at all.
Google for "site:reddit.com does seedvault even work" for dozens and dozens of examples.
why pad my opinions with outdated quotes if I can have first-hand experience? it's a good tip I gave on recent developments and your objections aren't convincing. Latest Lineage/Graphene both include in their forked seedvault repos a current enough version to check out d2d-transfer, give it another try.