The difficulty here is that the outline layout must accommodate both different fonts and different font sizes.
I believe the current layout for one-line items sets the baseline to allow for the descender height, plus the font leading, plus the added leading. That would give you different baseline heights for different fonts if the fonts have very different descender heights.
I’m not sure what ought to be done here. A similar issue occurs in notes: if the text is supposed to be visually centered in the note, what precisely is vertically centered? The baseline? The center of a the lower-case “x”? The midpoint of the tallest ascender and the lowest descender? I’m not even certain there is an optimal position in a world where some people use lowercase titles, some uppercase, and some small caps.