The traditional automakers are the ones making the regulation, trough lobbying (in the good and bad sense of the world). There isn't a regulation passed on the car industry that the car industry isn't part of writing.
I highly doubt that the traditional carmakers are slowed down by regulations.
Would be cool to find someone who has actual insights to ask this.
There are lots of mechanisms to fast-track changes. If Ford changes the headlight assembly on the next year Mustang, they don't go and crash the car again. They (or a supplier) fill out the certification form showing that their testing indicates the new headlight assembly abides by all the regulations imposed on vehicles, and submit it to the relevant state and federal bodies.
You can generally tell what revisions are straight-forward to certify and which are not by noting common year-to-year changes in a model.
I highly doubt that the traditional carmakers are slowed down by regulations.
Would be cool to find someone who has actual insights to ask this.