The decision to cover the Kanal window to prevent spawn killing is much more complicated than it appears to be.
If we placed an object on the ground, we saw that players would be funneled into choke points at spawn.
Furthermore, objects being placed around the spawn point were not sufficient enough to block line of sight from the window without creating other potential exploits.
After the announcement of the change, one of the first suggestions that we saw was moving the spawn point to behind the nearby building.