I've heard that "tight scalp" can disqualify someone from getting a transplant. Why?

[Centrino]

What is this condition? Is it fairly common, or quite rare?
How would one know if they have it or not?

[Hair Bear]

I would imagine this has more to do with FUT as it would mean your scalp would be even tighter due to a strip of your skin missing from you head and only being sewn up thus stretching is needed.