If this is not created to be transparent for the fans, it can certainly be speculated that there is a rehydration clause there in the contract being forced on Lamont Roach. However, this is not the fans' decision to sign the contract. If the offer on Roach's purse is high enough for the boxer to retire and if he is okay with this rehydration clause, he should sign the contract. But this would imply that he does not have an ambition to have a championship or a legacy in boxing.
If they do not announce it, people will guess there is a clause, and boxing fans will see this on the day of the fight. Usually, the fighter relaxes his body after the weigh-in and takes in more liquids and food, but he ensures that his speed and power remain, so at the time of the fight, we will see a fighter fighting in the lightweight division with the body of a welterweight.
We will see if the fighter has added weight, but if his features in the actual battle are very much the same as in the weigh-in, we can assume that the fighter did not put on weight and could be under the rehydration clause
I know that there are fights that we have seen how big the boxer are during fight nights, but it was before, it was during the time of HBO that we will hear the announcer telling what is the weight or how much a fighter rehydrated.
But now, I haven't seen or heard that stats or commentaries, maybe they don't want to tell the public or the data is not available for them to see that time. In any case, someone already says that there is no rehydration clause for this one. But I still think that Tank will come up the bigger guy here, maybe even fighting at welterweight or close to it during the rematch so that he will have more power.