5DII high ISO performance is much better than the 7D
Tuggen didn't say that the 5D2's high ISO performance is the same as the 7D's. He said that the 5D2's high ISO performance is the same as the 7D's per UNIT AREA of sensor
The reason why there are DSLRs, crop factors, medium frame format, is because the SENSOR SIZE DIFFERS
, not because there are more or less pixels.
Of course the 5D2 outputs cleaner images than 7D since it has a 1.6 ^ 2 times bigger sensor, but each square millimeter has the same noise level (I haven't checked this, the cameras' technologies may have differences since they are separated by quite some time, but it verifies for 1D4 and D3s).