I don't like to envision big because I would be too intimidated by my big vision to start small. Starting with a modest idea helps me keep things concrete. "Envision big" causes me to start thinking abstractly prematurely. I tend to not write much code at all when I do that.

I am sure "Envision Big" is implicit at least in this specific blog post.

Why? What's the danger in starting small?

The biggest risk is that you stay small, and given "small" in the context here also means "quick", how big a problem is that?