And Tor (and I2P) anonymity is not well characterized mathematically. Many argue they are not reliably anonymous. So if you argue against off chain mixing, you fail to note that your on chain depends on your off chain IP obfuscation, so your entire thesis of defense collapses in a house of cards.
You have made no point.
I made a very strong non-FUD point, which is off chain can layer multiple encryption. On chain just adds vulnerability and costs us a lot in terms of targeting mass adopted design factors.