How else would you describe Waymo's message?

Trying to "educate" or talk down to a competitor with words like "this is not how this works" when Tesla has significant resources, expertise (actual cars on the road!) and knowledge in this area seems defensive to me.

To be fair, Waymo (back then Chauffeur) have solid experience with Tesla's approach. They started with the same strategy of gradual improvements. They found out (and shard) the same issues Tesla is running into in the past years: Users don't pay attention when monitoring a system doing a boring task - even when failures carry a high price. Waymo switched the approach from a gradual L2/3/4 improvements straight to developing an L4 system; Tesla is locked in to the gradual move due to it being part of their business model, and are now stuck with trying to make self-driving work with unqualified test drivers (i.e. customers) and outdated technical decisions (not using Lidar because they were too expensive back then).

So Waymo does have the experience to call out Tesla here.

I recommend watching Lex Friedman's interview with George Hotz - its has some good points that one might should consider around the different approaches on reaching L5.