Should I be using separate device for calls and SMS?

Hello!
On some YouTube channels like The Hated One and others I've heard that you should not have SIM-card in your personal smartphone and use only WiFi instead. For calls and SMS you should use a much more simpler phone without access to Internet, GPS or WiFi. And in order to use your personal phone you would have to bring your personal pocket router with anonymous SIM-card.

So my question is: does this configuration increase your privacy in any way? …

device privacy sms