I am going to be that guy.
I make computers do things, but I never act like my stuff is the only stuff that makes things happen. There is a huge software stack of which my work is just the final pieces.
I agree with you in sentiment - the term "full-stack" is odd and a little too grandiose for its meaning.
But it is already established in the industry, and fighting it is unlikely to yield any positive outcomes.
The term "full stack" has a widely well understood meaning, you're being pedantic