Is this installation method okay?

Got a quote from an installer for installing REC panels on my flat tile concrete roof. He said they use a combination of sunmodo and unirac. The rails are apparently unirac. He said the sunmodo part is where they use a diamond bit to drill a hole in the tile, then use like a hook or something through it with some foam and then they place a metal tile on top of the existing concrete tile. He said the prefer not to replace tiles to avoid any damages to other tiles.

Thats my rough understanding, appreciate any inputs. The installer has great reviews online so I guess they know what they are doing.