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A co-linear mate is apply to lines (linear objects). The plane is a planar object not a linear object such as a line.
As TH says, Planes can take the colinear constraint. I believe I have made an enhancement request in the past to treat planar faces and Datum planes as equals when it comes to constraining sketches. You can sketch on a planar face; why aren't they considered equivalent otherwise? The ability to constrain directly to a planar face is also more robust than constraining to an edge which we are forced to do now, as the face is much less likely to dissappear as opposed to one of it's edges going missing, flipping direction, or changing internal ID. Pro-E goes about treating constraints in a heirarchy. It first constrains to surfaces (planar) before it will infer an edge constraint for this very lost reference reason.
Please make an enhancement request.