Smart Things & Google Assistant

I am planning on getting my ‘Security’ managed by the smart things hub, including doors, locks, etc. I started out using Phone assistants, then switched off to the Lenovo Smart Display with a few Home minis. Found out that smart home devices works so much better than phone assistants.

Problem is here, say locks and stuff, what prevents other people from opening them by just saying the command? And what are the devices that can be connected to more than 1 assistant?

the link smartthing - google link prevents unlock and disarm commands.

Not sue what you mean by this all my mini’s control all authorsied devices, any one in the home seam to be able to access my devices without having there account linked (eg kids)