Linus Torvalds needs the merge operation as an integrator.
Considering the email workflow of the kernel I can’t really make sense of “intended way to do it”. For individual commits people send out patches. I’ve never seen an email thread where some merge topology is recorded: it’s just a list of patches. A straight line.
I’m pretty sure that people used patch queues before Git (and even now with quilt). Restacking a bunch of commits on top of the mainline is the same operation as a rebase.
I’ve certainly seen Linus get mad at another maintainer for allowing a back-merge into his history (merge main back into feature branch).