I also agree that it has nothing to do with grain orientation, and every thing to do with bevel contact. It is true that the wood, in bowl/side grain orientation cuts differently when you are pushing straight across the bowl when compared to cutting down through the grain. Another explanation of that is if you cut straight across the top plane of the bowl, and when you are trying to go across the flat bottom of the bowl, when the end grain comes around, you are pretty much head butting it, and that can make your tool bounce, especially if you are pushing hard, which is common for heavy roughing cuts. When you cut from the rim to the bottom of the bowl, you are going down through the grain rather than head butting it, so the bounce is much less.
The kick back happens because you are not rubbing the bevel. So, straight across the top plane of the bowl your bevel angle should be parallel to that plane, and I will call that 0 degrees. If you come off the bevel to about 10 degrees, you will get minimal skating. If you come off to 30 to 45 degrees, you can get big kick back. When you go past the 45 degree range, the kick back starts to slack off. If your bevel is 90 degrees to the plane of the top of the bowl there is no kick back.
Flute orientation can play a bit into this. With flutes straight up, if you are not rubbing the wing bevel, you can get a catch. With the flutes straight up, you are coming very close to doing a scraping cut, or are actually doing a scraping cut. I always cut with my flutes on the side. Never related to the concept of open or closed flutes. Open flute to me means spindle detain gouge, which is ) shape. Closed flute is V shape..... Yes, I am more than a little different....
As for the rings in the bottom of the bowl, those come from a couple of things. One is the heel of your bevel. It is easier to control your cut by having the cutting edge as close as possible to the cutting edge. No problem on the outside of a bowl, which is generally convex shape. On the inside of a bowl, where the shape is concave, if you have a long/full length bevel, your rub spot is farther away from the bevel. This is why most bowl turners grind off at least half of the heel of their gouges. I prefer to grind off 3/4 or more of it. I also make sure it is rounded rather than a straight 'secondary' bevel. The other thing that contributes to the rings in the bottom of the bowl is pushing too hard. Your feet/minute speed goes down to almost nothing when you get near the center of the bowl, yet we all want to continue cutting at the same speed we do when we are on the rim. I have to bite my lip to make myself slow down and let the wood cut rather than cut the wood the way I want to. Again, the head butting that end grain contributes to the bounce, which contributes to the rings.
robo hippy