It seems that the synthetic stone is not the cause, but highlighting the problem: poor enforcement of safety standards and inadequate PPE provided to workers.
Just because there's more silica doesn't mean that it's suddenly unsafe whereas cutting granite is safe. Even drywall or cutting concrete you're supposed to wear PPE.
It never leaves your lungs though. In the last 20 years we went from "dust masks are for wimps" to "wow not wearing PPE is terrible". One small silver lining of covid is that even relatively oblivious home owners even wear PPE for small projects now. Smoking OR inhaling large amounts of dust might not kill you, but both are bound to make you miserable later in life. There is already a steep drop off in lung cancer deaths, peaking in the early 1990s. Right now we're down to about 1930s level despite having nearly triple the population.
You can buy a cheap yet very comfortable 5000 or 7000 series respirator from 3M for about $20 and the "pink pancake" P100 filters are another $12. If you're a hobbyist those ought to last you a year, maybe even 5 depending on what you're cutting. I do metalwork as a hobby and I can definitely feel it in my lungs (and taste it) the next day if the garage door is shut and I forgot to wear the respirator.
Cutting cement boards with a diamond blade is pretty god-awful for your lungs. On the order of few years.
Effects depend on the particle geometry.
But as a general rule of thumb: if it's biologically inert and tough enough to stick around for awhile... it'll just stay in your lungs. E.g. fiberglass, cement, rock, paint.
I wear a respirator a LOT more these days than I did when I was younger.
Just because there's more silica doesn't mean that it's suddenly unsafe whereas cutting granite is safe. Even drywall or cutting concrete you're supposed to wear PPE.