I've found GCP's UI to be a racy mess. If you ask it to do something trivial like removing an instance from an Instance Group, it can show that it has done it when, in fact, it hasn't. Want to switch projects? Better remember to hit F5.
How do you switch projects on AWS? In GCP it's a dropdown, in AWS it's completely different account (email or IAM or SAML backed) + captcha + MFA every time if not SAML.
AWS SSO [1] negates a lot of that pain, but still won't let you have two accounts open in the same browser window. You can use email/password logins or a SAML source like Active Directory.