So the question is, if those were not airtags but Google Pixel phones, would they sue Google for it?

I mean... you can do pretty much the same with Google Pixel and more. You can buy used ones for cheaper than an AirTag. And it does not require any special knowledge either.

About the only thing is that it is easier to conceal an AirTag and it will run for much longer, but there is no shortage of places on a car where you can be sure your wife will never look and many times you don't need for it to stay active for weeks or you have ability to charge it regularly making it only a bit of nuisance.