Hello,
You're certainly entitled to your opinion Chri5 and I'm sure you're aware that
quarry tile is produced by a high-pressure extrusion process. This forms a dense, strong tile that will absorb less than 5 percent of its own weight in water. You can use quarry tile on floors and kitchen countertops because it is water resistant, although not waterproof. Unlike porcelain, quarry tile should be coated with a protective sealing compound when used in applications that frequently expose it to water.
A tile is considered porcelain if it will absorb less than 0.5 percent of its own weight in water. Typically, porcelain is very dense and strong. For that reason porcelain is ideal for use in areas with lots of water like bathrooms, shower stalls or kitchens, or in rooms where dampness is a problem.
The surface of most ceramic and porcelain tile does not need to be sealed, although some require a light application of a penetrating sealer to fill the micro pores on the surface of the tile. However, the grout joint between the tiles is usually very porous and generally made of a cement-based material and should be sealed.
In the original post there's no mention to flaky grout. I agree that if the grout is flaky it should be replaced. I would also say that this could be a perfect opportunity to remodel the bathroom depending on budget.