I don't know why you lack the ability to read the wiki page explaining it, but, okay.
A stomp match is when a match is so unilaterally one-sided in the favor of one character to the point that the opposing character has 0 wincons. ZERO wincons. Which means, no chance at victory, absolutely 0 chance.
Meliodas has a chance to win, and thus this is not a stomp. On the contrary, it is a DECISIVE match, which means that the match is merely clear cut in one-sides favor even if the other side has a chance at victory.
Why exactly you require me to explain this concept to you is beyond me.