Yes, I was in the first category of people, where I am using GDNative to ultimately call a single function written in Go, not due to speed, but simply in order to leverage a huge amount of code I had already written in that language. Judging by the GDExtension headers, I can probably pull off something similar if I forgo all of the C++ bindings that I don't need. However, I am hesitant to dedicate any time to doing so at the moment.

Don't get me wrong, GDExtension seems awesome, but it's also true that it doesn't seem geared towards the case that I was using GDNative for.