Make a decision
Written exclusions versus verbal assurance
One scope
An exclusion shows what a quote does not cover, such as coil, burner, branch or repair work.
The other scope
A vague verbal promise is hard to compare or verify after the visit.
A concrete example
If a quote excludes the cooling coil, a later dirty-coil discovery is an add-on, not a broken promise. Make that exclusion visible before work so the comparison is fair.
Which question settles it?
Request the component list, access method and exclusions before approving an add-on.