I think you are describing this (SmartPlug) product ?
The 30A (twist lock) end of that adapter is specifically for marine applications, to keep the plug end of the cord from coming loose out of the shore power socket (boats on water can move quite a lot, where RV’s are stationary in comparison). I’ve not seen any RV site power panel that accepted a twist lock plug, but it is certainly possible someone *could* configure one in that fashion. I converted my trailer to SmartPlug a couple years ago but I only have a 30A electrical panel, so the adapter I have is the opposite direction (to allow my 30A cord to plug into a 50A RV site panel). I fabricated my primary power cords by putting the SmartPlug trailer side plug onto cords I already had, I did not get any adapters or cords directly from SmartPlug. When I bought my SmartPlug kit, it came as a mated pair of connectors (trailer side and cord end side). Hope that helps you.