No experience driving on a 'de aired' RFT, but my guess is: the '50/50 limit' is the tire mfgers being overly cautious and figuring 'everyone' lives in the 'Burbs and can get to their local tire store for a new ~ $250+ tire, combined with barrister buzz words and liability limits...
Otoh, a cursory glance at RFTs on the net did not elicit much info or success in driving well past the '50/50' limit.
Fwiw, I have one car that came with RFTs, (our '02 VetteVert), but the OE tires were replaced by non-RFTs after the original tires wore out. 8 yrs and 35,000 miles later I have never had a prob with the non-RFTs, though I do pack a plug kit and compressor in the large trunk well, in that car.
All anecdotal, but I have had my share of tires going flat, but in the past decade and a half those low air situs have all come to my attention 'in the driveway/garage' and an easy patch/plug job has taken care of the situ. When was the last time one had a 'blow out' or flat on a trip? Happens, but so does getting a hole in one.
RFTs have some slight benefits, (mostly emotional), but are really designed for Buffy's piece of mind, imo.
GL, mD
PS: My non tech opin is to not drive an AWD X on a de aired RFT for very far or very fast...