I guess I've discovered a bug:

Text elements align the same no matter if "base" or "bottom" alignment is chosen. The text is "shifting" (in both cases) when the characteristic "contains glyphs that cross the base line" is changed. Same shifting also occurs with text aligned "top" with having no glyphs reaching the top-line.
I assume this isn't the intended behaviour ...

For demonstration I attached a file where I've put lines (to align with) and three sample texts "as" (only "center"-glyphs), "aps" (glyph crossing base-line) and "this" (glyphs reaching top-line), each aligned with all vertical alignment-options (1-top, 2-midlle , 3-base , 4-bottom).

Hope fixing this dosen't take too much effort.
Regards,
Volker