Controlling the simultaneous safe movement of 3 receivers onto the hoses, making contact, refuelling, disconnecting and moving to echelon would be fraught with risk. 2 receivers can take immediate action if one threatens the other with inappropriate manoeuvring, but 3? Recipe for disaster. Also the air refuelling operator would have to monitor position, hose state, offload rate and fuel transferred - far too easy to make the wrong call to the wrong receiver.
2 receivers are fine, although I did once have to disabuse a clever bugger test pilot who thought that there was nothing wrong with clearing 2 receivers to make contact simultaneously.
AAR procedures have been developed to a consistent safe standard over the years. Reinventing the wheel is unnecessary!
That said, the US Navy did once refuel 4 x F9F Cougars simultaneously from a Convair R3Y Tradewind.
The Cougar had a wingspan only 6" shorter than an F-35B and although the Tradewind had a wingspan 10' shorter than the KC-46A, the outboard pods are about the same distance out from the aircraft centrelin. The event looks to have been rather....sporty.