https://drafts.csswg.org/css-grid/#resolved-track-list

A contiguous run of two or more tracks that have the same size and associated line names may be serialized with the repeat() notation.

I tend to think that the above sentence should be removed from the spec and that the resolved values should always use the expanded form, i.e one value per track. UAs are currently returning incompatible values: Edge use repeat() syntax and other UAs don't. It's a burden for script to have to deal with two formats. I think one-value-per-track is far easier to work with so I propose we settle on that as the mandatory format.