Well, I don't have the definitive answer for the original question ...
But I have some 'maybe-interesting' info which definitely falls within the realm of second-hand rumor. Maybe someone else participating in this thread can shed some further light on it ... and I'd appreciate hearing whether any of this stuff was in any way accurate ...
So ...
Listening to someone connected to the agency, who claimed some sort of knowledge of what was happening when the decision to adopt the 10mm cartridge was made ...
Supposedly somewhere within the FTU, some sort of internal review/report had just recently (prior to the Miami-Dade incident) been produced which was a review of handgun calibers suitable for use in the foreseeable future, and it had been determined that the .45 ACP was not going to be among the future of viable choices. Something to that effect.
Then, since nobody enjoys being wrong, obviously the .45 ACP couldn't suddenly be selected when it had just been deemed unsuitable, right?
New people at the helm later ... and what was old is now new again. Dunno. Not at all. Anybody else who has closer knowledge other than rumor have any thoughts on this?
Like I said, I have no idea is remotely connected to the actual events, but the fellow seemed rather bemused and disappointed with how things had happened when it came to the selection of a 'better' cartridge than the W-W 9mm 115gr STHP used at the time ... even though it wasn't the only caliber/ammunition used in the incident.
Maybe ... and I wouldn't be surprised ... it was merely another of those rumor-control stories which can take on a life of their own. More than likely the case.
Naturally, the 9mm continued to be used afterward, although in the heavier 147gr OSM load, as well as other heavier bullet weight 9mm loads over the years. The Federal 190gr JHP 'Fed-Lite' did eventually give way to the 180gr .40 S&W ... and most of the rest, it seems, is history.
I dislike rumor, though. Maybe sometimes entertaining if it's a harmless sort of info sharing, while sitting around enjoying a cigar ... since sometimes there is some small particle of fact hidden away within the folds of rumor ...