I have a random guess about the problem with the alternate, bearded Boimler: he’s actually William Boimler, who killed (or imprisoned) Bradward and took his place on that Cerritos for mysterious Section 31 reasons.
That Boimler even says, “nobody deserves to be replaced by their own double.”
I also wondered about the possibility of the transporter double, though one who choose to grow a beard like Riker's as opposed to taking his name.
Hopefully though, if there are any Boimler S31 concerns, it will be specific to the William Boimler from the prime universe.