I haven't measured, but my sipo dominos slide in and out much more easily when dry fitting. They are nice and snug but not tight. For the beech dominos, I usually need to use pliers, and sometimes pliers combined a few side taps from a mallet, to remove them.
I had thought it was because I was using the beech on 3/4 inch plywood versus using the sipo in solid wood. But, I do live on the Gulf Coast, and it is usually very humid in my garage. Maybe the beech swell more.
Some have suggested putting dominos in the microwave before using to shrink them a little. Haven't tried that.