Yeah, people are probably going to notice that their data is now just gone long before the blanked drive becomes useful for Chia. If they wanted to use it for Chia they would have just used the free space and left the data intact so the owner of the drive doesn't have a massively obvious flag that something is wrong.
On the other hand, if people don't notice their device was wiped and don't take it offline after a day or two, it would be an indication to the hacker that they can safely store Chia plots there for a while, over the entire disk space, without fear of losing them soon.
Regardless, according to that Ars Technica article it seems the actual reason was rival hacking groups trying to steal control from each other, so it was a hack wiping another hack, and indeed most likely not Chia related.