GarretJ, I a tally think he is correct here. Irrespective if he is right or left handed and I'm only aware of humans playing cricket although some players do behave like animals sometimes!
Anyway, pls try this quickly. Move backward using only your back leg, as you suggested.
Then try pushing backward off your front foot. I think you will find the second movement to be much more efficient. Secondly, I do not think he was encouraging him to plant his front foot but rather to have his weight on his front leg.
Having your weight on your front foot is planting, it's the reason Chris gayle struggles with shorter bowling on comparison to anything pitched up. It's also why his foot movement appears sluggish
Stand one one leg tell me which leg allowed you to move forward?? Obviously the back leg.
Its simple to answer your question.
dip your front shoulder and the weight simply transfers to the front foot and your head is now in the forward position. You are ready to go back without leaning back.
I have a few questions.
If you forward press to a bowler who is bowling 80mph away swingers and he suddenly throws in one that cuts back into will you be in a nice position to play it?
If a bowler strays down the leg side or on leg stump can you easily move forward to on drive or not play around your pad?
If you forward press and need to go back how do you transfer the weight backwards with moving your head from the forward position in your stance?
I can tell you 100% that at the higher levels if you plant your front foot early you are going to struggle a lot. At a lower level you will be find but why not practice like the pros even if you are only subject to recreational cricket where the bowler is 65mph maximum, it would make batting a lot easier.
Back on subject
You must hold your front leg in as long as possible with a small amount of weight still on your front foot but more on your Backfoot. Say 70/30 just before delivery stride. Not a big back and across just a small step to create the unweighting of your front foot.
All you need to do to go forward is lean in and push off your backfoot. If you stay like this you can easily on drive as you are not committing your front leg and having to play round it which can also cause tipping over.
So I would say stay still or go back and across if you can keep your head still but never forward press.