They modified that position a bit later. https://www.everydaynodaysoff.com/2010/01/25/shoestring-machine-gun/
^ 1) see above. 2) to an integrally suppressed weapon whose barrel is purpose made for it and and itself the suppressor: Actually it is.
"Actually" may be interesting, but it's "legally" that matters. For purposes of NFA 1934, a suppressor is a firearm, and based on ATF's own numbers is in common use for lawful purposes.