Evidence, or it isn't true.
Unrelated, but absence of evidence is not evidence of absence.
Anyways, your own statement:
Adtech relies on the OpenRTB 2.5/2.6 spec for tracking, you would have removed 1 identifier out of a hundred (one that isn't really used anyway given SSAI is so popular).
Removing an identifier that is used. (1/100 = matters, "isn't really used" != unused). This contradicts your other statements:
Yeah, multi-hop is pointless for tracking.
...IP addresses and multi-hop don't matter...
Broad statements that don't take into consideration the threat model of other users. Servers you connect to might not be using source IP in any way to track. You might be leaking so many other identifiers, that its completely useless to worry about multi-hop. But this is not true for everyone in every situation.
If its worth anything to you, the Tor Project seems to think multi-hop and IP addresses matter for protecting against tracking.