I have to believe ATF is purposefully being misleading with their current web page language on serial numbers and other "info" on homemade guns. On the previous version of the ATF website the language regarding sale and distribution of homemade guns was fairly clear but the info on marking and serial numbers was a little unclear.
The result has been all the same questions and misunderstandings that we see every time a make-you-own-receiver thread comes by; "you can make it but you can never sell it", "it has to be serial numbered', and on and on.
Given that ATF had been ambiguous in their published guidance, you would think they would have looked forward to wording things clearly this time around. But nooooooo, it's worse than ever. The law hasn't changed but the ATF wording would make you think it has. They have even gone so far as to change their original wording that used the term "individuals [who make their own guns]" to use the term "manufacturers" leaving the implication that only manufacturers can make guns or that anyone who makes a gun is therefore subject to the laws governing manufacturers.
It would not have taken a master wordsmith to write the "homemade gun" guidance in perfectly clear language. Instead, ATF chose awkward language that obfuscated the law even more. So, one asks the rhetorical question, "Why would they do that?"