Every time you use a treadmill you lift a foot onto the deck. If the deck sits eight inches up, that is a step roughly the height of a stair riser, performed twice per session, often while the belt is stationary and your weight is on one leg. It is a small thing on paper and a real barrier in a hallway.
Sunny Health & Fitness publishes a floor-to-deck height of 4 inches for its extended-handrail treadmill. That is the only machine on this site that states the figure at all, and it is why that one leads the treadmill shortlist despite being the most expensive walking machine here.
For flat pads the step-up is effectively the overall thickness, so it can be read off the published height — about 4.3 inches on one Sunny pad, 5.2 inches on the Yesoul. We mark those as derived in the spec panels, with the reasoning shown, because the manufacturer did not label it that way and we are not going to pretend it did.