What actually belongs above the fold on a trades site
The person looking for a plumber at eight in the morning is not researching. They have a problem, a postcode and about fifteen seconds. The first screen either answers them or it does not.
Three things answer them. What you do, where you do it, and how to reach you right now. Those fit comfortably above the fold on the narrowest phone in circulation, in type large enough to read outdoors.
The things that usually occupy that space instead: a slideshow of stock photography, a paragraph about the company being family owned since 1998, and a set of accreditation badges at 40 pixels wide. All three are true and none of them is urgent.
That material is not wasted, it is misplaced. Trust copy works hard on the second screen, once the visitor has decided you do the thing they need. Leading with it asks them to care about you before they have any reason to.
We build the phone layout first for this reason. If the three things fit there, they fit everywhere else with room to spare.