Does model space have units? 'Cause I spent a couple years receiving files from landscape architects and architects and having to decipher through deduction what the model units were and if the blasted layout was even actually drawn 1:1. Got it spectacularly wrong once.
In the past officially only files saved as blocks had units but a lot of people used $INSUNITS for files that are not blocks. More recent versions of autocad have a setting for units but a lot of long time users still don’t use it or know about the new setting.
My wish, related to this topic, is that when I import a file and find that I picked the wrong option (either because I was incorrect about what units the file was created with, as happens with stl files, or when I pick the wrong option about scale or not scale) is that I could UNDO the units change after I import. I sometimes have files that take 5 minutes to import, and then I find they are scaled incorrectly, and then I’m stuck either scaling it in Rhino (not always confident that the scaling factor has enough digits or that my trims will not be messed up by the change) or re-importing the file.
I’ve been using AutoCAD since V2.6 and as far as I can remember, it always had a units setting. Architectural (feet & inches), Decimal, Engineering, Fractional, and Scientific. Of course, you could make a drawing and never know what units you were using if you didn’t bother to look. I imagine it would become obvious when you tried to add dimensions. The Decimal setting is especially vague because then it’s up to you to define what a unit means. Parsecs anyone?
I haven’t used autocad for about 20 years so it’s a bit foggy now but I used it without any problems transferring to Rhino and the CAM program I had back then. Working in the UK every file was in mm and non of the programs tried to do anything clever like scaling imports. Then I got a couple of programs programed in and for the US market that assumed all DWG files were in inches and scaled all up by 25.4 and the trouble started.
I seem to remember you could set the units for paper space and the scale used to reference model space and you could set $INSUNITS for DWG blocks but a lot of programs ignored the setting. Rhino for example does set $INSUNITS but doesn’t seem to read it if you re import a DWG\DXF.
I use Fusion quite a lot now and at least a couple of times a month someone using AutoCAD complaints their imports are the wrong size and when I open the file the units are not set and they have no idea how to set them so I guess setting units is still not as easy or obvious as it is in Rhino.