Double Salchow Training?

[RosiePosie.iskates]

Are Double Sals okay to practice off ice?
I've heard that the only off-ice jumps you should practice are axels because all other jumps require a draw-in or edge. Also if you practice toe-jumps off-ice it leads to bad habbits. Is this true?

[hopskipjump]

Dd's coach had her do 2s extensively off ice.  He showed her how to do it and would check to make sure it was done correctly.

[Skittl1321]

I only do singles, but my coach has me do all jumps, including toe jumps off ice.

He showed me very specific ways to practice each jump to mimic the entry.