When TNT is activated by Flint and steel, the TNT-animation move one block to the side, -1 on X coordinate in my testing. However the particle effect does not move. I assume it's a visual glitch during the rendering of the animation as the hitbox doesn't move with the tnt-animation but with the particle effect. The animation also glitches into blocks if activated next to (a) block(s).
My testing has been both in creatif and survival, only in the overworld, one default world and one superflat, not in water nor lava and without any other entities involved in the tests.
I hope the screenshots provided are of some help.
Good Luck.