Would it be normal on a broken in 100cc twin engine to be able to grab it by the hub and turn it through compression by hand with medium pressure?

Hard to say, everyone does not turn the prop the same..Really slow rotation will let the compression leak past the rings and turn over easy, fast rotation just the opposite...Take a cylinder off and look at the piston, check for a ring stuck in the groove or brown on the piston below the rings...Either condition is not normal...

Yeah, i should have been more specific. Should an engine turn through compression easier once it's broken in?

No..New rings leak slightly until they seat in, the compression will get better with use....

thanks.

I learned a technique from a former user on this forum. He told me to take the propeller and flip it hard against the compression and not through it and the propeller should bounce between the compression strokes fairly easily. I have a BME 102 and it will hit against the compression stroke twice and rest against the third. A friend of mine has a BME 102 and I tried it with his engine and it did it 4 times and reseted mid-way through the travel. His engine is a lot stronger than mine.

Now two points do not make a trend, but I don't have any additional information to go on or engines to test.