Happens all the time in the AR15 world. There are far fewer actually manufacturing components than there are names stamped or engraved on the receivers.
Any shmuck can buy a laser engraving machine and start offering their own "house brand" lowers. There are not as many mass manufacturors of lowers as people think. Even fewer makers of uppers. (though yes, anyone with deep pockets can buy themselves a CNC machine and start making limited quantities of recievers).
In reality, many of the "brands" peope nit-pick over (which is 'better', ect) are actually made by the same foundries and simply assembled at different locations.