I already answered in the sales thread where you asked this question.
The inscription regatta on the dial is simply a symbol of the connection of this special series with a particular regatta, whether it be Laureus, PCYC, or others.
If we are talking about functionality, then formally, only models with P.9100 / R can really be practically used for their intended purpose, while the PAM371 submersible with the GMT function will obviously not help if you participate in this regatta, just as the PAM230 wouldn't help in the Olympics.
Initially, this is just a marketing ploy, giving a reason to make some changes in +/- common models, and sell them for a much higher price within the SE.