Good idea, too! Why do you see my explanation as cynical, though?

Your explanation is literally "blame somebody else, shift responsibility". It's a pretty straightforward case of assuming bad intentions.

Obviously, I don't know for a fact what Anthropic's motivations are, but I don't believe I'm being overly optimistic because I know for a fact that "use a third party as a way to de-risk" is a tried and true strategy. E.g. when I was at Facebook, all regular day-to-day comms were on Workplace, but they kept an IRC server hosted by some vendor or other, specifically to coordinate responses for serious SEVs that disrupted the normal channels.

Of course, an even simpler explanation is that they perceive building their own support harness as just low value work for engineers who could be working on their core product instead, and the cost of buying that service from somebody else is probably a drop in the ocean.

A cynic is what an optimist calls a realist.