Yep. Since grooming is a mutual reinforcement of the bond in a herd of chins (or rabbits, horses, dogs, greater and lesser apes... lots of creatures) I've always figured it was some kind of "your turn" behavior.
Tinkerbell does the same thing. We go back and forth we me giving her scritches, and her grooming my hand, my arm, my feet...whatever is closest to her!
I agree. I guess Trixie felt I needed a lot of grooming last evening when I had her out for play. She sat on my head grooming my hair...and then onto the picture on my shirt,
Several of my chins groom me in return. Roo will sit on my shoulder and groom my hair and eyebrows all the time...but he does expect scritches in return.