I certainly understand your question; I've also wrestled with the issue of which words to include in Nemeth mode.
After conferring with people more knowledgeable than I, I can tell you that if words are part of a math expression, they are math. So, something like "Perimeter = the sum of the side lengths" should be in Nemeth mode.
For the "Units of Time" list on page 562, I too would include all its components in one big Nemeth mode.
Units of Time begin Nemeth
60 seconds (s) = 1 minutes (min)
60 minutes = 1 hour (h), etc.
100 years = one century end Nemeth
As for your note on the TN page about graphics being in Nemeth, I believe you could use that note and then not include switch indicators around the graphics. Personally, I would not do this; I would include switch indicators around graphics if they are in Nemeth mode, with the reasoning that this would be more useful to the reader. Regardless, you do need to follow all the guidelines laid out in the Provisional Guidance within a graphic transcribed in Nemeth mode (including guidelines regarding words).
Thank you for your well though out and well presented question. If you have further concerns, please do let me know.
edited by kdejute on 11/15/2015