CR Draft - 4.5 Line Areas

In para 3, the description of nominal-requested-line-area states that "it has
the same block-progression-dimension for each line-area child of a block-area".
Doesn't this require that each line-area child have the same nominal font (i.e.,
the same font-height)? I may be missing something here, but, but I would expect
different line-area children to not necessarily have the same nominal font.