For the Sox, those were 3 very different teams, so yes. The Spurs were a little more constant, but I agree. I think the Yanks 10 in 15 counts.
I also don't think 3 championships makes a dynasty. 4, barely.
Using that criteria, maybe there were only 6 or 10 ...
1) Celtics (11 in 13) and I'm not even a Celtics fan
2) Yankees (10 in 15)
3) Canadians (10 in 15)
4) Bulls (6 in 8)
5) Packers (5 in 7)
6) Edmonton (5 in 7)
7) Yankees (4 in 5)
8) Steelers (4 in 6)
9) Islanders (4 in 4)
10) Lakers (5 in 9) barely counts