Wow, that is a short ratio. I think you're grinding a bit fine there, even for a ristretto. I'd be doing 20:20 - 20:30.
I was taught a proper ristretto was in the neighborhood of 14g yield where a regular pull is 28g yield. Admittedly, I do (personally) up-dose beyond the more conventional 18g of a "double" dose. To that point, the dose and grind are also a function of how the machine functions.
The Linea PB I used to work on was far different than the Classic (semi-auto) machine.
Regardless, that is the challenge and adventure of Espresso!
Whether at home or in a Cafe, it is the "simple" goal of finding the right balance where all components come together: bean, environment, grind, machine capabilities, and the dose and tamp...
I'm doing 18:40 in about 28 seconds
To me,
that is a long pull! Not to be confused with a lungo which would be 18:60 in about 60sec, by my understanding.
One thing I learned in my barista training is there is a lot of variation, whether good or bad, in the world of coffee. Even among "good" coffee shops.
The important thing is we love it, still, and we know what we like when we get it!