You must not realize what they sounded like in 1969 before they recorded their first album.

Jerry made weird spaced-out sounds come out of the pedal steel and there were extended jams. The record company was liberal, but not stupid. Hence, the commercial nature of their first record.

BTW, they didn't really open for the Dead in the early days. The Dead mutated into NRPS by having Pigpen, Kreutzmann and Weir leave the stage, being replace by John Dawson and David Nelson. Jerry moved to pedal steel.

The did not become a stand-alone unit until later.