Yes, the two situations you cite are clearly stated and this makes them easy to remember and to follow with confidence. Thank you for pointing them out to us.
I think the situation that has many of us wondering is, do we leave line 1 blank on a new braille page (without a running head) when a "change of thought" new paragraph begins? [That is, if there is any braille on lines 24-25 of the preceding page, and the new paragraph uses the same cell pattern? such as 3-1] A print book would put centered asterisks (for example) at the top of a page to indicate a break in thought, even if centered asterisks were not used within a page to indicate such. What if displayed material begins at the top of a braille page and there is braille on the preceding page on line 24 or 25? Is the indented margin enough of a clue that this is displayed material? Or must line 1 be blank there as well?
A blank line 1 seems quite unobvious to me. Is it noticeable to braille readers? It is surely does not speak as loudly as a blank line *within a page. Regardless, we would all love to see a simple guideline we can turn to when faced with this layout which --as you say-- occurs far more frequently than one can imagine is possible.