Butyl Tape vs Dicor Self Leveling

I am about to install a Fantastic Vent and replace the skylight over my shower.

The skylight manufacturer says specifically to use a butyl sealant that comes in a standard caulking gun size like the Dicor does.

This started me thinking, I used to use butyl tape for all seals on my older RV's.

Why can't I just use butyl tape under the new Fantastic Vent and be done with it? Butyl tape also doesn't react with rubber roofs at all.

Seems like less of a hassle and no re-sealing every year.

Your thoughts.