Transaction broadcast is a completely different issue than scanning. One shot Tor connections are a nice potential way to deal with that.

Dandelion would be nicer, but so far nobody has implemented it in a DoS resistant matter. Part of the problem there is that the Bitcoin Core mempool is already extremely complicated, though I'm still hopeful that will improve, e.g. with cluster mempool.
https://github.com/bitcoin/bitcoin/pull/29415