It’s been asked many times over the last few years, but so far they have been reluctant to do it because many of the dimmers on the official compatible device list, such as the GE switches, only go down to 10% increments. So there’s no harm in asking, but I don’t think they’re going to do it.
You can use smaller increments if you use webcore or some of the other unofficial rules options instead. See the following (this is a clickable link)
How to Get Started Creating Complex Rules in SmartThings (2017) (SmartThings Classic)