It doesn't matter to me as I personally don't bother and outsource the job - that's the point.
Usually I watch a YouTube video or two about what a plumber probably needs to do so I don’t get totally ripped off.
If a business does not have any understanding of the competencies mentioned in parent, they are at a huge risk of being ripped off by outsiders.
Then you have a "trust" problem which is another matter.
That is pretty much the nature of the beast with contractors; not another matter. If you don’t understand what they’re doing at some level, they’re probably just using you for billable hours. If for no other reason, they have other more demanding clients that actively manage them.