that's no myth, Will.
thing is, in practical terms of the line's performance the level tip doesn't help much for turnover.
it leaves us with a 'flat spot' between the end of the line's front taper and leader butt.
the longer that 'flat spot' is the more detrimental it is to energy transmission.
for optimal performance it's best to reduce it as much as possible and configure the leader butt diameter from there.
cheers,
marc