They're subsidizing their tokens as long as you use their software. That's a fair exchange, I never understood why people took issue with it. If you don't want to get locked in to Claude Code, you can pay more. Just like you can pay more for an unlocked non-carrier subsidized phone. (Which I personally do.)
The issue with this kind of subsidy is that it is designed to lock you in and not as a loss leader. In other words, it is not like giving free nuts at bar to make you drink more beer but more like Nestle giving baby formula so that the babies get use to that instead of mothers milk
Also, not everyone uses their plan to the usage limits; the idea of a prepaid bundle being better value if you commit is not novel.