Writer indents and spacing in "ch" and "line"

users
#1

LO 7 introduced a new way of thinking about, and sizing, indents and spacing in Writer - from definite units of measure (inch, mm, pt, ...) to "ch" and "line" of a reference style's font characteristics. I'm sure there's a reason for that change, but still have not found it, and have not even found how it connects to such reference style (set in the Page style).

I read the guide on "Page Line-spacing Printing" but don't find it on-point, as these new measures apply whether or not page-line-spacing is activated in the relevant Page and Paragraph styles. Can someone point me to an explanation of the reason for, and use of, these new units of spacing?

Thanks,
John