Requiring to see the property is very common during the re-assessment appeal, and all the property, too.
Unless the only homes comparable nearby that sold were actually brand new, your assessment should be fairly close to those, for same size, beds, baths, number of stories, lot size, and maybe garage. Even a 7 year old home would be considered comparable to an unrenovated, but well maintained older home of the same size.
If your valuation is comparable, but did not include the basement finished area, you will run the risk of an increase in your assessment. It does happen.
I have seen properties be reduced in valuation for things like placement on a busy road, or an issue with the property, or evidence of damage inside.