We are now in a crucial part of the conference but San Miguel needs win because they lost a lot when June Mar was out. In order to get that wins, they do not need anything that could disrupt their established play by inserting Romeo in the mix. Romeo will not be able to score a lot yet coming from a long vacation in basketball, so it is best he is given the least minutes for now. He can be full-time in the next conference. Not disrespecting Romeo, but it is what the team needs right now.
Much better to activate Romeo in the semis if they can make it. At least in the semis, there are a series of games where Romeo can do some adjustments unlike in a few game series in the Quarterfinals. I understand your point that activating Romeo right now might destroy their current momentum. It's different in Fajardo's case since The Kraken is not a playmaker while Romeo shares the role of some of the key guards of the SMB right now.
And according to some reports, if Romeo will be activated, Coach Leo Austria will remain on the sideline and he will allow his deputy coach George Gallent to take over since according to Coach Leo, he doesn't want to destroy the momentum between Romeo and Gallent. Honestly, it doesn't make sense to me.
Maybe there is a chemistry built between Romeo and Gallent whenever they are practicing. I don't know as well what Coach Leo means with that phrase "destroy the momentum between the two". Well either way, they already got a spot in the playoffs so putting his deputy coach on the driver seat and giving him an opportunity is also good for the team.
With regards to Romeo playing against Meralco, they already secured the 5th spot and will face Meralco regardless of what happen, so I think putting Romeo to the court to play for a few minutes doesn't hurt the team as a whole. They will just let him play a few minutes in preparation for him during the playoffs. Fajardo and Romeo's situation are completely different. I don't know if SMB has the weapons to beat Converge TBH because they are a strong team as well, but let's see how they will play.