ATF is dealing with 290,000+ comments for receiver rule; and still plan to issue it in June 2022. Previously, they dealt with 36,000~ comments for bumpstocks.
Meanwhile, the FAA is dragging their feet on only 19,000~ comments for the Boca Chica EIA.
This does show that volume of comments are not an obstacle if the rule/process is heavily desired by those at the top.
My personal hunch, which is sadly unsupported; since I don't have any contacts "in the know" is that elements are nudging the FAA to "thumb the scale" just enough that SLS flies first.
If SLS flies first, even if it only beats Starship by a week, things will be great.
If however, Starship beats SLS -- that's going to be quite uncomfortable, because remember, back in 2014, then NASA Administrator Charles Bolden said:
"Let's be very honest again. We don't have a commercially available heavy lift vehicle. Falcon 9 Heavy may someday come about. It's on the drawing board right now. SLS is real. You've seen it down at Michoud. We're building the core stage. We have all the engines done, ready to be put on the test stand at Stennis... I don't see any hardware for a Falcon 9 Heavy, except that he's going to take three Falcon 9s and put them together and that becomes the Heavy. It's not that easy in rocketry."
If both Falcon Heavy AND Starship fly before SLS; even the dumbest congressman will start asking hard questions, which will be rather uncomfortable.
Yes, I know there are elements who want Starship:
DOD is warming up to it's potential to rapidly deploy satellite constellations; a vital national security need as space weaponry becomes more prevalent, while the NASA Science community is warming up to the idea of HLVs, as long as they're not the one paying for HLVs. (SLS is a threat to science, because SLS funding sucks away money for science spacecraft).
But they don't have enough influence (yet) to be decisive. I think what we're seeing here within NASA and other government agencies associated with space is a generational switch comparable to the "Bomber Mafia" of the 1940 to 1960s, which was slowly supplanted by the "Fighter Mafia" post-Vietnam in the US Air Force.
As I said before, I can't prove any of this, as I'm an outsider looking in, with no contacts within the bureaucracy.