How vpn chrome extensions works together?

Hello, I have several vpn extensions that usually are on together. They cover some holes in each other access. However, my friend said that only one proxy can work at once time and proved it with chrome proxy settings. So, my question is, is there any exiedence that proxies can switch between each other when they can’t open site? Because words of my friend conflicts with my reality.

Example:

  1. We took test subject VPN. I can’t get access to several sites with it.

  2. We turn on other vpn. Off and on subject VPN last so chorme display it as main in settings.

  3. Site is now accessible.

  4. Off other vpns except test subject, ctrl+f5, site is not accessible again.

Checked on several problematic sites with different test subjext vpn. So, who is right? My friend said I don’t understand how vpn works (he neither tbh), and google can only use 1 vpn. In contrary, I think there is some kind of switch settings in chrome to “delegate responsibility” between apps.

Ideas?