I'm having the XLE with JBL, please see if this can resolve your concern.
I used to drive a Mazda CX-30, I like to adjust the instrument brightness to maximum and it will still auto dim instrument and infotainment during night time.
Seems Toyota or our Cross is not having the same logic as Mazda. After I picked up my Cross, I adjust the brightness to maximum and it was too bright at night, same as daytime and no dimming.
Then I found that if the brightness set to maximum (the dial / switch at up most position, you feel a click and locked) the auto dim will not work, it always at 100% brightness and blinds me, ha ha
Try turn down a little bit, you may feel the click and then you should have the auto dimming. So now I try turn the dial all the way up but stop right before it "click and locked at full brightness". Then I have like 90% brightness and both instrument and infotainment dim at night or go into underground parking.
Not sure if this is in the user manual or I misunderstood, but I couldn't find it...