Yes, it is tail walking. The early stages of tail walking is much as you describe, but the nose is lifting and with enough speed and wind (+ apparent wind), the board will take off. Almost all boards will do this in the right circumstances even with a small fin (wind speed, smooth water, wide board, sailor weight, size of sail, point of sail (beam reach or higher).
With enough skill to hold down a 7.5 on a beam reach on a 135 L board in 30 knots on flat water with a 40cm fin, a 90 kg sailor will probably stay on the water, but a 70 kg sailor will be in the air.
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.