Like with boob jobs, slim women with big boobs exist, mature men with great hairlines exist. So there's always that sense of not being sure if that was indeed the case. I generally don't assume boobjob except in overtly crazy cases.
I've never seen anyone who is mature that had great density and was a NW0, there is always some recession of the hairline even when the hairline itself is dense. Even if I could get a NW0 hairline I'd probably opt for a NW1 but I'm probably getting ahead of myself here, still years to go and for me at least replicel may be good enough.