This part is not necessarily correct. As I said in my post above, I have finished 3 basements in houses we have owned and did all the work myself and never considered a permit. Sold all 3 with no issue, the last one in 2019. The listings all had the finished area in the basement listed and ran into no problems in central Iowa anyway.
I will say, I am aware in some big cities (Minneapolis and some surrounding cities, specifically), they are non-negotiable when it comes to permits. Before you can sell your house, you have to do a "pre-sale inspection" by the city. And they are 100x more nitpicky than your typical home inspector. They will also challenge anything that has been improved and not in their records. I know of cases where they have made folks open up drywall to expose unpermitted electrical, for example.