If the center of the platform is 6 o'clock, then at what location do you place your single step? 9 o'clock (if you are right handed)?
Gotta have a system and stick to it. Here's my system...
Climb system (bolts, screw-ins, or sticks) is always on the right side of the platform (usually about 4 or 5 o'clock) which is my weak side. The top step will be slightly higher than the platform. Having that step below the platform is totally useless during the hunt. The extra 18" in platform height isn't doing anything towards being higher and out of being winded or seen by deer. I don't understand what the mindset is for having the top climbing step lower than the platform.
My single step on the strap is always on my strong side and placed at about 8. The size of the tree will dictate exactly where I put that step. I might put it more toward 8:30 on a larger tree.
I always have at least one foot on the platform. Transferring all body weight off the platform and onto the step on the strap contorts the strap positioning which can effect the cam-over of the platform. If full weight is repeatedly transferred from the platform to the strap over the course of the day things can shift. Keeping ~50% of body weight on the stand ensures that it will stay positioned and tight on the tree right where I originally put it. Straps stretch, too. So I'm only putting as much weight on the strap step as I need to.
For me, there are 3 uses for having a step just off the side of the platform. The primary use is for a little more body control getting around the tree. Whether it's for hiding behind the tree, or positioning around the tree for a shot, I have much better control over ultra slow movement if I have a step out there. And its definitely more comfortable if I end up half way off the platform for a long period of time because of of deer presence.
The 2nd reason for that step is that I just shoot better. Yes, I can shoot 360 without the step, but I shoot more accurately if I have better control over my body position, and that step helps me with that.
The 3rd reason for steps on each side is just for comfort. I find platforms to be the most comfortable for extended hangs, but even platforms can get a little uncomfortable after 4 or 5 hours of having both feet restricted to a 1 foot square area. It's a nice change up over the course of the day to have a foot rest that's located just above each side of the platform. As a footrest, having the step set level with the platform doesn't work as well as having it set 6 or 8 inches above the platform. And having them set below the platform is totally useless.
I like when a piece of gear can due multi-duties. Having the top climbing step set below the platform relegates it to being nothing more than the top step. But having it above the platform allows it to be part of the climbing system, and part of the movement control system, and part of the comfort system.