
I have never heard of true ratios or false for that matter. But the important thing is that it does not matter. As long as you use the notation in the way you understand it consistently you are in good shape. The explanation that 1:10 means one part in a total of ten parts seems unecessarily complicated, If we are going to use scientific notation, we would be talking about solutions with a precise specific gravity, or solutions with molarity, molality etc, etc.
In the end if you make 1 part in 9 or 1 part in 10 the difference is so slight as to have no impact in processing, so people, just do it the way you understand it and do it that way always and you will be fine...