I'm a heel to tip kinda guy. For some reason I get better results for stability when starting with the flatter heel section of a knife. I guess it's all a matter of what feels better to you because the method you use most is the one that is most comfortable and most likely to produce consistent results. A fair question though, I've often thought about this myself.
I played around with an idea similar to this a couple years ago. The idea was to finish a knife on a 2k stone but squeeze more out of it. So, I finished the edge using only one direction edge-leading strokes starting from the heel. After the edge was done, I went back and did a handful of edge-leading strokes starting from the tip of the blade to "cancel" out the scratches left by the previous direction. It actually did work, the edge was indeed a bit finer than the standard 2k!
I noticed this effect while I was doing body and paint for years, sanding on cars. You always sand in an x pattern because it knocks down high spots better, but you will also notice that it seriously reduced the size of the scratches from the previous direction... up to a point, then you completely start new scratches. But, there is a point when you are crossing another scratch pattern that you can nearly perfectly cancel out both scratch patterns and end up with a nearly scratch free surface, or at least free of any deep scratches.
When you are sharpening you are always starting from one side, the heel or tip. This will inherently make you do an x pattern over the stone. At the edge, this x will certainly help refine the edge, but you are still left with single-direction scratch patterns on each bevel. Normally we just use finer stones if we want to decrease the scratch size, but my experiment was an attempt to decrease scratches with a single stone, without the need to decrease pressure as well.
So, reversing directions for the last few finishing strokes can have a different effect on the edge, but the question is are your hands steady enough to perfectly match the bevel when changing from heel to tip or vice versa? Honestly, this experiment was more out of curiosity for me and I never do it anymore on knives... but I actually do use this technique when finishing my straight razor. I more-so use this technique stropping my straights to ensure I catch all parts of the edge, not so much to cancel scratches. Under .5 micron I don't know the benefits of trying this as the scratches are so fine you are probably actually surpassing the grain size of the steel at this point and your real enemy is edge burnishing.
My personal opinion is that this technique has a more noticeable effect on anything under 4k due to the more noticeable effects of cancelling larger scratches.
I think as humans doing free hand sharpening, we should always focus on consistency more than anything, that's what produces the best results IMO. I'd be interested to see a few other people try this, it's most easily done on a nakiri IMO as it's easier to maintain consistency from end to end when changing directions. Glad you brought this up, it was fun to remember and share something almost long forgotten.