Your projects still being there is intentional.
You can still build them with the new user, but the new user will have different certificates, so you will need to be careful submitting to the store. You will need to remember which account built them and use that same account to rebuild and submit updates to the stores.
If you want to remove the list of projects so the new user does not see the old users projects, delete the contents of this folder, (or just rename the global-settings.xdk to something else)
C:\Users\USERNAME\AppData\Local\XDK
