Where are you taking lessons (what kind of studio/dance place) and where are you planning on dancing? There are different versions of salsa; ball first is more "ballroom", flat is more "authentic"...and... I'm going to leave it at that. Heel lead is just plain wrong.
I'm sure that someone who is a Salsa expert will step in, but I believe that you will encounter the full foot version more if you dance at Salsa clubs.
Where are you taking classes (you asked about taking them as follower in another thread) and what do they teach there? If they haven't gone over the foot work, watch how the teacher demonstrates steps.
Essentially, flat foot for forward steps, is correct, however, the "ball" of foot, has a very slight preference, as weight is taken.
The danger in using a completely flat foot, is being back weighted, if the body "pitch" is not correctly aligned.( think " inside " edge ). Weight distribution in salsa, due to speed of music, should be always towards the ball .
For the poster.. be very careful about learning from vids.
As to heel leads , not uncommon in some styles, and, there are occasions in salsa where a heel is used .