In my experience geese will eat pretty much anything. They are particularly keen on the rubber handle of my trowel, the bristles of the brush I use to clean out the poultry houses and my baby apple trees. In fact, they'd probably pick any of those over a whole field of fresh grass. To be fair, I don't think they actually eat them (except for the apple trees) - they just like chewing different textures or something but they can be surprisingly destructive. So, no, I don't think it's an indication of anything worrying. I think it's just an item of interest.
I would give him (have you only one goose?) some pellets (e.g. waterfowl growers/finishers) as well if grazing is poor. That will ensure a slightly more balanced diet through the winter than just grains. I give pellets in the morning and mixed poultry corn in the afternoon at the moment. Geese really like corn in water so at the bottom of a bucket or bowl if you've not tried that yet.
H