Maybe, that claim is pretty speculative and shouldn't be repeated as established fact.

I agree with the rest of your points, though there were a lot of proxies other than tor. In particular, there were well known forums you could post on to get private proxies -- often used for kinda shady astroturfing and similar. So excluding tor alone isn't sufficient. Tor wouldn't have been as useful for Satoshi's bitcoin usage because he couldn't run a node over it that accepted inbound connections.