Yes, I understand what it technically means. But please refer to the part of my post that I bolded. "As applied to ball python morph names"...the term "het" IMPLIES one half of a matched set. So if you say, "het lesser" you're implying that the animal has one half of the set needed to make a lesser.
I'm not disputing that a lesser is a heterozygous mutation. I'm just saying that I don't believe it is accurate to refer to the animal as "het lesser."