Yes, SDR is less efficient than a specially designed radio chip, but what you gain is flexibility. With SDR, your radio can use any transmission encoding, you are mainly just limited by your polling rate.
Specially designed radio chips thrive in constrained, high-volume manufactured devices. However, for development purposes, being able to use LoRa with an SDR is an amazing step up.
If Musk had legitimate criticism of the bill grounded in facts, then I believe it would have been perfectly reasonable to make an attempt to try to influence lawmakers. The issue here was the use of misinformation, influencing lawmakers to make decisions contrary to what a factual argument would lead them to have made.