Lots of ale yeast on top?

[Richlandbrewer]

So I have been doing AG (strictly ales, 5 gallon batches) for many years, fermenting in the standard 6 gallon plastic buckets. My experience is that when I open it up (after a week or more), the top surface is beer, with some yeast chunks floating around, which quickly migrate to the perimeter and stick to the side of the bucket as I drain it into the bottling bucket.
Lately I got a chance to obtain a stainless steel vessel with a shallow cone bottom that is about 15" in diameter as opposed to my plastic buckets which are slightly less than 12" dia. So the "aspect ratio" of the stn. stl. fermenter is much different than the plastic bucket, with the wort mass being "shorter" than it is tall.
Anyway, I have used this (the stn. stl vessel) for fermenting, and I end up with a significant layer of yeast on top after fermentation is complete. So much so that I decided to skim it off prior to draining it into the bottling bucket. The beer turned out real good, but I am mystified about the difference between the two approaches and would really appreciate any insight as to why there is such a difference between the yeast sitting on top versus settling to the bottom.