Odd, I cannot find a way to reply to another member--I can only see a REPLY box at the bottom of the page so it looks like I'm replying to myself when posted.
The M-477 does not come up when searching All Forms at https://www.uscis.gov/ and clicking at top Forms followed by All Forms on the left.
I think I'll give up on the convoluted website and just stick with what is asked in the N-400 online application. The checklist at https://www.uscis.gov/n-400 contains only a few items vs. two full pages for the Nov 2016 version of the M-477 (which is also found on the same page under Forms and Document Downloads).
I even found another version of the Nov 2016 Guide to Naturalization, M-476, which clearly states it is out-of-date but could be useful. Looks like they are shorthanded to the point they cannot update to current--at least someone had the diligence to make the out-of-date note.