Years ago, we applied grout sealer that we got at a big box store to a backslash that was installed around around our kitchen and around a sink in the laundry room. No mater what got splashed on the tile it always just wiped off with a wet sponge. Whether it was tomato sauce or beet juice in the kitchen or grease, dirt or oil in the laundry it never left a stain. Unsealed grout can be difficult to keep clean. In our retirement home, which we moved into 3 years ago, we had a tile backslash installed that's marble. We had that sealed since both the marble and grout would stain. The prior owners told us that the bathroom tile was sealed when it was installed. With that said, I'm not familiar with the product that Jon mentioned.
If you have an open mind, you’ll generally find that you’ll learn the most from the people who say the things you least want to hear.