Yes, I have several grafted sumo scions on many of my trees and some are 4 yrs old. The taste of the fruits will get better on the older trees. I do see half of my grafted sumo with fruits which may look ripe (fully colored orange) but if you taste them now it is still not sweet. It's edible but just a little sweetness and mostly acidic. Here's another fruit I picked a few weeks back that looks ripe, let it sit on the counter for 2 wks to see if it gets sweeter but not really. Still needs to hang on the tree until Jan-Feb here for me in SoCal.
My older branches have much larger fruits and they are still green, probably will not turn color for another month. If I wait until end of Jan to mid-Feb the fruits taste seems to be the best. Last year I waited until March but the fruit was past it full ripeness and it wasn't as good as the ones from Feb.
Here's the flat sumo fruit I picked, no seeds, and ate on 12/17/21. Still not sweet, but more acid taste as Goyo said.