That is an abuse of the term ratio!

Nonsense. One can do either, depending on what you want. (Loosely, and
using moles rather than grams, one give molar-type solutions and the
other gives molal-type solutions. But this has nothing to do with the
OP's question; no chemist would use ratio terminology in describing
either solution. (by which I mean, they would not use the :
terminology. They use an explicit description, such as M, which means
moles of solute per liter of solution; or m, which means moles of
solute per kilogram of solvent.

I find the OP's question interesting. And most of the replies have
been quite unresponsive. I am not a MT, but do teach chemistry. How to
state dilutions seems to be confusing -- the point of the original
post. My own preferred solution (no pun intended) is to state
dilutions as to how many-fold they are, eg, a 2-fold (2X) dilution
(which I would call 1:1), or a ten fold dilution, etc. Describing
dilutions that way is unambiguous. Using the ratio symbol seems to
have become ambiguous, if not simply wrong. So simply for clarity in
the real world, I would try to avoid the ratio terminology here.

bob

(snip)

Having worked in more than 10 institutions in my career, this is an
important distinction to make during initial training.  Different texts,
different facilities, different departments, and even different SOP writers
use the symbol in their own way, but you can usually guess the correct way
by its usage.

In the field of Med Tech, we use professional judgement alot -- a 1:10
dilution using MLA pipettes becomes 1:11 when you only have a gray one and a
blue one!

Larry