He'll probably just say that mate x got drunk and shagged a sex worker or random, that he can't have the kit delivered to his own house because of his wife /gf and that he, being the great guy he is, got it for him.
Whether that is anything approaching the truth, is another matter.
(I'm sure most people could get a relative to have a kit delivered to them, or get it delivered to work, or a collection point if they were desperate to avoid a partner not seeing it).
Also that would mean they cover up for infidelity among their group.
The very fact that no gossip etc has come your way about this stage do via the men on it and their partners ....which is what usually happens, the men blab, their partners get angry, they talk to the other partners if they know them ..... Means these guys are a certain level of cheaters and betrayers; not the low level ones who don't much but feel guilty and can't keep it from their partners and blab; which is what I've seen stag do attendees often do. They're the higher level, discrete, water tight ones.
Either that or the partners haven't told you because they don't want to be accused of "destroying" a relationship and causing a wedding not to happen.