At current transaction rate, it will take 100+ years before we get the same workload than the spam.
In other words, the spam blocks contain 100s of outputs and the current blocks only a few.
Any available sync algo (including sdk before SbS) work with the current rate.
I would say that the main focus should be to increase usage (real not spam).
Another issue is that users rescan when there is any problem. And because by default the rescan starts from sapling activation, they have to process the spam.
Monero has encoded the birth height in their seed phrase. I think it was a great idea.