Question about SNGs and fluctuation

[Chaostracize]

I have a friend who is a very good SNG player. I say this after having talked about numerous hands with him and seen him play. He is currently playing the 215s.

I was just informed that over 5,000 SNGs he has an ROI of 6%. I think before any conclusions can be made regarding skill that more the person in question should play more SNGs, but he disagrees stating that the 6% is an accurate represntation of his skill and he just isn't good enough to be playing at the level he's been playing at for months.

Is there a satisfactory conclusion that anyone can come to?

I know this really comes down to a simple variance and bell curve post, but I think that this player has simply been getting unlucky and over the course of another 1-5k games his ROI should be easily around 15%.

Thoughts?