Microsoft has every right too.
They don't need your consent.
They certainly can, they have the legal grounds to, but it's richardish to do something that will potentially be causing problems without the users consent. Many users have legitimate reasons for not upgrading (In which case it's pointless to force it upon them and can cause inconvenience due to the extra space taken), and many users cannot spare the harddrive space. It would do more good to have it only be downloaded when the user says "Yes, download it and install windows 10"
Honestly this really isn't a big deal. It's good to know, and I actually had the folder so I deleted it manually. Now I have room for an extra game. Convenient!