Siri-Read Messages require unlocking

That allow Siri when locked is not for Siri to read. However, with the settings you have, I believe Siri should be able to read your messages. I cannot test mine right now, it is too late at night for me to get any messages. I can test it again tomorrow and respond, or you can wait for someone else to respond.

What other posts are you referring to? If you go to Settings>Notifications>Messages, do you have Show Previews turned on? I believe it has to be set to Always for you to be able to allow Siri to read Messages.

What setting are you referring to when you say you have Siri set to read when locked? The only Siri setting I find in Accessibility is about voice feedback.

My iPhone XR had the problem of needing to unlock my phone while trying to listen to messages from my car. The mentioned settings fixed it but since I've updated to IOS 13.1 the problem has returned. All of the settings are the same. This is not safe.

Do you have Messages set to preview? I believe you need to have that on for Siri to read messages.