Reply To: box at top of print page AND top of braille page
The blank line that precedes must be the line immediately above the text it is preceding. If the item begins at the top of a braille page, there is no place for the blank line. You found exactly the wording that covers this--A top box line can appear on line 1 when no running head is used. Note that when a running head is used, the top box line is on line 3, not line 2. The same iks true for headings, which require a preceding blank line as well.
The only exception is certain instances in which the adding a blank line at line 1 is the only way to show a change in context from the previous braille page. These instances are relatively rare. A new blocked paragraph, for instance, that happens to start at the top of the next braille page would require a blank line at line 1. When the beginning of displayed material or the resumption of regular text after displayed material occurs at the beginning of a new braille page, there also might be a need for a blank line at line 1. That may have changed with the new guidelines, because displayed material is now indented. I haven't looked that one up yet.
The guidelines says speficially that opening box lines and headings can go on line 1. That's what it means.
--Joanna