trouble with opentype small caps after upgrading from InDesign 2019 to InDesign 2020

I'm slow to upgrade because of issues like these, but I was recently working on a file in InDesign 2019 and one of my paragraph styles uses small caps. For 2019 and earlier, my opentype fonts use opentype small caps when I select "Small Caps." This selection would use both the correct uppercase and small caps for lowercase characters only. But now in 2020 and 2021 (I just checked it out), I can only get the opentype small caps to work when I select "Opentype All Small Caps." This is a severe design limitation since I wanted to use proper small cap characters for running heads in a book, using text variables. I don't want to have to start using new master pages for every chapter again. In case it's relevant, I'm trying to do this with the font Mercury Text G1. Does anyone know any work arounds or when this issue will be fixed?