Right now it seems that Pro does not save options related to scale-based sizing with style items, and turns it off when applying a style if you had it on. In other words, if you save a symbol that has 'Enable scale-based sizing' checked and go to apply it to another symbol class, you'll run into one of two issues. If that class has scale-based sizing already turned on, it'll be turned off and your settings removed when applying the new style item from the gallery. If that class is not using scale-based sizing, it will continue to not use scale-based sizing, which may be unexpected if you saved a style item with scale-based sizing.
I feel that it should instead do one of two things: save and apply scale-based sizing with style items, or just leave it alone. Quit turning it off if I had it on. Choose whether style items should include scale-based sizing settings or not so we at least have consistency. Right now you have to re-add your scale-based sizing by hand every single time you change symbols which is quite irritating.
These are the settings I'm talking about.
