Have been looking for info about differences with sRGB profiles – just check yourself
- X-Rite: -What is the difference between "ICM" files and "ICC" files?
- Capture NX: Nikon sRGB or sRGB IEC... ?: Nikon Pro DX SLR (D500, D300, D200, D100) Talk Forum: Digital Photography Review
- Are "Nikon sRGB" and "Nikon Adobe RGB" the same as the Real Thing? - Photo Tips @ Earthbound Light
Most probably I used this one
from PL4 as well then as Custom profile.
The ‘club competion entry’ you mentioned, should recognize all sRGB variants and maybe it filters out the extension *.icm.