I have a Deco mesh configured with the guest network enabled, and the password is 10 chars but fairly simple. The Deco app keeps warning me that this is a security risk.

Isn't the guest network logically isolated?  Unless the Deco is designed badly, no one should be able to get into the router config from the guest network surely?  So why is this a security risk? Do TP-Link not believe they have an effective firewall between the guest network and the router / the main network?  I appreciate that you can never be 100% confident without a physical isolation, but even in corporate environments you tend to have a level of trust in logical seperation?