I downloaded it yesterday evening. It’s experimental version fd5dcb5 if that’s what you’re referring to (with the custom autopilot).
As you mentioned, that’s how it was for me before the update and before deleting it. Idle was around 19% and if I kept it around 21%-22%, it would keep a constant speed while taxiing, around 20 knots.
I departed most recently from KPDX (Portland, OR) and at idle thrust (24% for me) I was taxiing at 25 knots pretty quickly.