I used a flat grind up until very recently. Now I use a hollow grind. I find no difference at all in the way chisels or irons cut. I would not expect to find any difference. The actual cutting edge is identical.
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I find the angle of the bevel, the angle of attack and the sharpness of the edge is what makes the real difference.
Even the opposite of a hollow grind, the convex bevel, is advocated by some and seems to work for them.
It may be you came upon a sharpening epiphany during the class and didn't realize it.
Only a few of my tools retain much of the hollow grind they had when they came to me. One in particular has only about 1/8" of the hollow left on a quickly turning flat, long bevel.
Don't get me wrong, a hollow ground bevel is a great help in picking up the skills of hand sharpening. That in itself may have improved your sharpening skill.
jtk