Of all the candidate ASOS frequencies (below 121.75 or so, perhaps?), what
would cause the FAA to choose the same one for two nearby airports?

For that matter, why do Long Island's Easthampton and Montauk have the
same CTAF? (16nm apart) That's a real pain in the arse on a busy
weekend day... or under IFR... I know there are only so many freqs
available - maybe make MTP's PCL freq the CTAF? Just my .02