Yeah, it's a killer feature, but I really wish they had some sort of a documented "search API".

Instead of natural language search, where I have no idea whether it understood me, I wish I could do (modifying your example):

"North Carolina" "Maggie Thomson" "Tom Morgan" -beach 2018

for all photos in NC, with Maggie and Tom, not in a beach from 2018

and even better, if it could tell me the number of results that would show up if we removed each keyword above.

I guess it's a tough problem, even for Google :(