True, you can download an .acsm directly. If it hasn't already been registered to an Adobe ID, it will work.
That is okay for OverDrive ebooks, since they expire anyway

but purchased books will be foreverafter bound to that Adobe ID, which you don't have the password to, which means the books will never be accessible to any other device/app/computer... and youd better be careful not to deauthorize it either.
NOT WORTH IT!!