The two kinds of window get confused constantly, and the confusion is expensive in both directions.
Why it matters
An arrival window is a promise we chose to make and can choose to loosen. A service window is a fact about the site. Treating a real access constraint as a soft preference produces a wasted visit. Treating a soft preference as a hard constraint spends route flexibility that was never required.
Commercial work is where this bites. A kitchen that can only be treated between two and four is not being difficult; it is open for business the rest of the day.
How you notice it slipping
Both kinds live in the same field, with no way to tell them apart. Technicians arrive and cannot get in, repeatedly, at the same sites. Or the office refuses perfectly workable appointments because a long-ago note said “mornings” and nobody asked why.
What to do
Record them separately and say which is which. Then ask, once per commercial account, what actually governs access — opening hours, staffing, a shift change, a health inspection cycle. The answer usually turns a vague restriction into a workable one.