Once all the interconnections are figured out and the mechanical engineers know what needs to hold what shape at what temperature and pressure, and the metallurgists know what chemicals will be touching the metal, and the power connectors to sensors are all numbered so you know how many you need and where they'll go, and the communications lines with what format and inputs/outputs they'll talk to at what voltage... to me a spec is the document that tells everyone where their little part needs to fit.

You have to do that downstream and collect it back upstream for larger projects, since the person doing it never has enough expertise. And then the spec negotiation between teams that don't really necessarily know what constraints each other has which need to be resolved so that people know what to design.

It's frustrating but actually writing down a detailed spec really does enable a lot of other stuff to happen. I'm sometimes blocked as an individual because of a team that's in my path but which isn't really in my field. Say, they do optics and I design the optical sensor so I need to know the optical power to expect but they have to do simulations and get information from the chemists and semiconductor test engineers first. I need a spec for what they want -- I need to know how low the light level is, how much noise there is, and lots of other little details too.

I don't know if that qualifies as "terribly meticulous" but in my experience skipping the spec step often means wasting an incredible amount of time solving the wrong problem.