My opinion...which mostly matches what I've seen in the field...
Does a person with electrical knowledge and certification need to be present when the racks are constructed ?,
No. And definitely not when the work is digging holes and pouring concrete. Electricians shouldn't even be allowed to do that stuff.
On tilt-up racking, my answer is 'No', since the modules can be plugged in by someone else later.
On flush-to-the roof mounting, connecting modules usually has to be done at the same time as setting the panels, so see below, but my answer is still 'no'.
or is such a qualified person not necessary until actual wiring takes place?
A qualified person is always necessary.
Whether any certifications required should be those of an 'electrician' is another question in my mind.
Wiring arguably falls into two parts; wiring on the array, and wiring between the array and the inverter(s), the tie in point, or other arrays. In my opinion, the qualifications necessary to do wiring on the array are not sufficient to call someone an 'electrician,' nor should someone be required to have all the skills and knowledge of an 'electrician' to do that work. OTOH, when the wiring leaves the array and enters a raceway, that is electricians' work.
In my opinion if a law requires a certified electrician to set panels and connect them only to each other or to micro-inverters, that law is unreasonable. I do not believe that in California the law requires that.