Marty, in all due respect to your region, which is also the place of my ancestors, I can't imagine there is much there that isn't MDF, except in antebellum mansions.
Tile and grout cleaners swell it often, but for whatever reason don't often get in trouble for it. Perhaps people don't notice unless its severe.
There are certain things I've found when I visit peoples' homes socially:
1. Most carpets have resoiled quickly after cleaning.
2. Most upholstery has water marks around the piping and skirts after cleaning.
3. Most MDF baseboard is distorted after tile and grout cleaning.
I've learned not to point it out, as I hate to get people I like in trouble.