The PAM1389, like the original PAM389, is also 47mm (sorry for my earlier response on the same question, I was talking about availability of the watch, not the size). It is slightly thinner because of the different movement. As for the comment on the rep trend of comically big PAMs, you should realize that factories usually only follow the trend in the gen world, as reps imitate gens. The last SIHH put 47mm submersibles front and center, so it's but natural for the factory, specifically VSF, to but replicate the hot models.
But don't despair, the 42mm PAM960 is coming out. Also you can try looking for the PAM682, which is also a 42mm submersible (PAM684 if you're into rose gold), which were released for quite a while already.