[Phileleutherus Franciscus]

He wrote a treatise on the arbitrary nature of assumed coordinate systems; is that what you’re recalling?

I think I see the error. You are confusing his explanation of why non-Euclidean geometry was necessary for general relativity to an argument that "all coordinate systems are equivalent".

If that's the case: reading comprehension fail.

[editor-surveyor]

Obviously you’re in the dark. Carry on.