How do I stop my text messages sharing to all my devices

if what you claim would be true, what is this option for on my iphones with latest OS to this date:

can't find the pattern, sometimes text messages won't forward for a few days then it forwards them all again at once.

This can be considered a security risk because if the mac gets compromised and a MFA request is sent to the phone, access can be granted to accounts only for the specific mac.

Sign out of Settings/Messages on the devices where you don't want to receive messages. You can't stop just text messages.

That is a change in the latest IOS. What I posted above about signing out should still work. If you are signed out of Messages on the computer, you shouldn't receive any messages.