Yes, your right. Ive just installed it on a new device with a new set of credentials, and the multi device feature is on by default (which it shouldnt).
It definitely shouldn't be on by default. It's just convenient to have that feature, but in exchange for security risks. Definitely not worth it in my opinion.
I hope the application features contained in this application are more complete than those of Google
It is. Google's 2FA basically has little to no features besides the 2FA functionality itself.