[css-grid] Is span keyword excluded from Named Grid Lines <custom-ident>? #494

The "7.2.1. Named Grid Lines" Section defines the syntax as just

[<custom-ident>*]

Where CSS Values for <custom-ident> says

Specifications using <custom-ident> must specify clearly what other keywords are excluded from <custom-ident>, if any

I would assume that span should be excluded not to collide with Line-based placement properties

Am I correct?