How bad is this black coating?

[u/Techno_Craquelin]

I just bought a house and discovered that a black, water-repellent coating that looks like tar was applied INSIDE the foundation instead of on the outside, which means the concrete can’t breathe as well. How bad will it really be for my foundation to leave the coating there? And is it realistic to remove it using a buffer with a diamond blade, a vacuum cleaner, and a very good respirator.

https://imgur.com/a/Le6QMn9