lessc.cmd cannot find @import file, path resolves fine?

Question

The above code displays the following error:

cmd.exe /D /C call C:/Users/<user>/AppData/Roaming/npm/lessc.cmd --no-color style.less
FileError: '/styles/vars.less' wasn't found. Tried - /styles/vars.less,D:\projects\ui\themes\default\styles\vars.less in D:\projects\ui\themes\default\style.less on line 1, column 1:
1 @import "/styles/vars.less";
2 


Process finished with exit code 1

But if I change the path to something invalid:

Now I see "Cannot resolve file" as well as the unresolved variable. Is this a bug or something I'm doing wrong?

Here is the folder structure of the relevant files:

(root)/
├── styles/
│   ├── vars.less
├── themes/
│   ├── default/
│       └── style.less (the file with the error)