An intention question requires three initial checks: 1. What kind of act is involved? 2. Does its time function as an envelope or a measure? 3. What degree of specification does the law require in this exact circumstance?
A person who abstains from eating for health reasons raises the question whether worship was intended at all. Someone who intends to fast but does not name the specific kind of fast raises a different question about required specification.
Treating both as a single undifferentiated “intention present or absent” problem can produce a false conclusion.