Wreckage is a unit. Creating wreckage should not (as far as I can tell) change the cell type of the tile where it is placed. The code that detects wreckage, as far as I remember it, has a bug in it where it can fail to detect the wreckage unit depending on the cell type.
So changing the cell type doesn't delete the wreckage, it just makes it invisible due to the detection bug. You can probably set it just once, either before or after placing the wreckage to hide it (or reveal it).