HFY has only 'one' SNT. The variances you might see will depend on what is being focused on in training at that time. Say you have been to X workshops focusing on X different subjects, certain portions of the form can be 'performed' differently to help the student understand and drill what is being focused on. This is easy to see if you look at the form conceptually vs. just seeing the techniques themselves.
When looking at the out-to-in ending part of the 'heun sau' portion of section one, one might say "hey, that used to be a faat sau to gaan sau!" and the answer might be "it is faat sau, if we are focusing on faat sau kiu sau, but now we are focusing on [fill in the blank] so it is a different shape (say leet sau instead of faat sau), but same idea". The concepts don't change, just the application within the context of what is trying to be taught at that moment - and this can easily be reflected in the from.
Sometimes a SLT solo drill can be made to help further understanding. I still hear people say "but this is different than the from", again, same reasoning. What is it you are trying to learn at that time? Techniques, or something deeper :)