Maybe I misunderstood it but I never got the idea this was case , they will not charge for the previous years. Just that to continue to use it you need to pay, and that applied to already released games. It’s not exactly the same as you mention

In any case as other comments said the previous terms covered that case so yeah legally they cannot charge them for those already released games if they still use the old unity version, as the terms allowed for somebody that doesn’t like the new terms to stay on the older version and the older terms.

But as I pointed out in another comments that generally don’t works because sometimes the devs need to update the games for fixes on the engine to support new hardware or stuff like that or simply fix bugs on the engine itself.