[nl]

No, if I understand Drew's statement correctly:

They have a system they use for IP enforcement that bans based on file hash. They used this system to ban the files.

A side effect of this system is that it sends a DMCA notice to anyone who has a copy of that file hash (because that has always been what it was used for before). I'm guessing inside the hash-ban tool there is a field "owner" or something, which they filled in as "Dropbox" and is used as the source of the DMCA notice.

I don't think there is any conspiracy here. Never ascribe to malice what can be ascribed to incompetence. I's pretty harsh to call Dropbox incompetence, but given how it would make sense for their system to work, I think a mistake is a fair description.