The real answer is obvious, like the media that doesn't know the difference between a bayonet lug and a sling swivel, apparently some Congresscritters have confused the bayonets and such with the deadly "shoulder thing that goes up".
None of the features they have targeted make any sense, except for mags. At least that one is geared toward the function instead of the look that makes Nancy soil her Depends. IF it passes the only thing they will have accomplished is make an incentive to introduce new designs like the KelTec SU16 that utilizes existing mags in a "sporting" configuration. Just like last time, unintended consequences the idiots who dream this stuff up never consider. When the mag ban hit last time the gun makers responded by making handguns sized around a 10rd magazine, or less. Millions more easily concealed small handguns now exist just for that very reason. Coincided with the wave of right to carry laws across the USA, so everyone benefited. OOPs, Nancy just soiled another diaper......