If it sounds overzealous, consider things like

"Positioning must not obstruct visual or physical access to aircraft controls and displays, flightcrew ingress or egress, or external vision'

So all the certification requirements mean somebody had to map out where it goes and how. Including CAD drawings, any recurring maintenance tasks, research on sub-supplier quality, troubleshooting procedures, a reliable replacement supply chain, and so on. And have all that reviewed, documented and approved for each type/subtype of aircraft it's certified on. If the process were more lax, it's not hard to imagine a problem with pilot visibility of some control (or whatever) starting a bad chain of events.

I could be wrong, but I think the more time-consuming part of certification is initial certification of the procedure - a company (eg a company that offers modifications to aircraft owners) will gain certification for their ability to perform a specific procedure on a specific aircraft type. They can then do that procedure on customer aircraft. I believe the certification of the aircraft itself is less time-consuming; more of a confirmation that the approved-upon procedure was followed.

I'm just curious, how does it work in practice?

Is there like a huge number of FAA government employees that sit around waiting to be called up and then they are all flown out to some location where they frantically flip through binders of rules to validated everything is up to spec?