I just use only my pinky finger as well. It never felt natural to have my ring finger down so I didn’t force it.
The main reason why people say you should put two fingers down is because that’s what Earl Scruggs did. The issue is everyone hands are different and what works for him won’t necessarily work for everyone else.
I’ve seen people play really well with jut their pinky down, just their ring finger down or using both.
I recommend picking one of the three options that feels most comfortable to you.