Yeah the best way to get you to think about pretty pink unicorns is to tell you to NOT THINK ABOUT PRETTY PINK UNICORNS.
The place to learn the giant stride is in the pool. Trying to merely describe this procedure is bound to produce erroneous results. Some people "get it" right away and some don't.
However, once snickering or overt laughing starts (it NEVER is totally behind their back), the need to save face shows also starts. Add to this a Divemaster YELLING at them over air consumption... AIR CONSUMPTION and we have an environment that fosters this saving face phenomenon.
Again, I first fault the original instructor. Her buddy/planning/entry skills seem to be lacking or non-existant. Possiblyher instructor was as abusive as the DM and if so, I can see that she merely emulated her instructor's attitude.
The problem with giving advice, is that it rarely respects the privacy or dignity of the other person. Start with "I see you are having some difficulties with your giant stride, and I would like to share a few things that my instructor passed on to me..." The response to this question will clue you into a few things. Whether they SEE they have a problem. Maybe they LIKE the face plant!?! Whether they are open to YOU. Whether they are open to ADVICE from you.It is better to show empathy than outright contempt.
Again, owning a card without owning the skills is an instructor problem, not a student problem. Students almost ALWAYS perform to the level of skill required by their instructor.