watching BMX videos id say your wrong, BMX is prob easier to get started at maybe, but i wouldnt know where to start with tail whips etc.
and DH i think its a case of anyone can do it, its just pretty hard to good (fast downhill) at it.
watching guy ride DH an he looked on the edge, ever corner i thought he would stack it he was going so fast. then steve pete came down, smooth as hell, looked a lot slower...but a good 2/3 secs faster :P:S
each sport is different an hard in its own way