Yes, they can,  however you'll each need to sign into the app before doing a test.

To find the log out option, click the three lines top left of your screen and the menu will slide in from the left with these choices:
  • Home
  • Account
  • Scale Settings
  • Help
  • Sign Out
click Sign out to exit your account and the app will revert to the sign in screen.

The other person can now sign into their account.

To check who is signed into the app at any time, click the three lines to access the menu and click the Account option.