I believe this is not correct. I believe there is no government mandate to disable a receiver above a certain speed or altitude. I believe GPS receiver manufacturers will certify certain receivers for flight navigation and they prefer to sell those to a pilot than to have him using a non-certified receiver.
Actually, it's more complicated than that.
GNSS receivers with certain capabilities are classified as Munitions by various countries and as a result are subject to Export Controls. So if you include a GPS receiver in your product which has capabilities beyond these limits then you end up needing an export license to be able to export that product. In the US, until a few years ago this included an altitude and speed threshold of 60,000 ft and 1000 knots. These were called the "COCOM" limits which was basically the name of the regulation that led to these limits.
I am not sure if there are any remaining rules globally as to speed and altitude. I know that in the US there are still certain limits such as "GNSS receiving equipment specially designed for use with rockets, missiles, SLVs, drones, or unmanned air vehicle systems capable of delivering at least a 500 kg payload to a range of at least 300 km" but there don't seem to be hard limits anymore. But since much of the software has these limits coded in them, then it's sort of stuck around.