To inspect the pump you would have already removed 3/4 of the stuff required to change the timing belt, so that’s why when you do the job the timing belt and water pump go together. If your timing belt was done in the shop and you have documents you could call the shop. It would be borderline negligent for a shop not to replace a pump when doing the timing built IMO.
I don’t think you could do a visual inspection to determine condition just by looking at the pump cover.
If you’re unsure and the mileage is getting up there since the timing belt was changed I would go and re-do the job this time with the oump