...... for fishing dry flies you *want* the tippet to sink into the film.
--
Ken Fortenberry


I'm sure the "track" of a greased leader is very visible, probably worrisome, to fish.

Years ago, George Harvey stuck lengths of HEAVY leader into bugs and
dropped them into a stream. The trout took them readily. His
conclusion: It ain't the sight of the tippet that scares the fish,
it's the drag.

You can read about this in both of George's books. I believe
Marinaro also mentions it.

vince