Ah, but a board in chop with enough speed does "skip" over the surface with no displacement for a short time. However, I agree with your point. If you watch speed sailing runs that Antoine Albeau and others have made on very flat water, the boards don't seem to skip as you say, and it looks like displacement is consistent.
When they do "blow up" or leave the water, the crash usually begins with a spin out. Small fin with too much force. However, I do believe that at some point, it's possible for the apparent wind to get under the board and lift it off the surface of the water. This isn't too likely given the narrow, short boards plus the heavy sailors with weight jackets all designed to keep the board on the water to prevent "take off" (and to allow the use of larger sails).
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.