You are right! Oh, wow. Now I feel dumb. I got away from using numbly for the section numbering, because I wanted to have the possibility that my sections start from section 0, which I can achieve manually but not with numbly, so I didn’t think of using it for the enum-numbering, but instead adapted my section numbering to also work there. Thanks for the anwer!
If anyone is numbering, the full equivalent code is:
#import "@preview/numbly:0.1.0": numbly
#set enum(
full:true,
numbering: numbly("{1:I}.", "{2:1.}", "{3:a})","({4})" )
)