To be honest, I got a bit embarrassed at my error with regard to the “src addr” thing, so before writing my reply, I injected packets into
- a Mikrotik (running 7.191.)
- an Ubuntu machine modified to run iptables
- an Ubuntu, as stock, running in iptables-nftables compatibility (as has been the default for many years now)
- in all instances the route the packet took was according to the ingress interface.
Then I went and looked at the source code: lo and behold, you can guess what I found.
So it’s clear that “from self” is the correct one.
The “dst addr=own addr” thing is a bit simplified but largely accurate. (I still think “to self” would be better, but the “dst addr” one is at least accurate enough.)
EDIT: Yes, I hate being wrong.