Why did my phone add someone to a group chat without my input

I have an iPhone 15 Pro Max running 17.2.1. I will use names to make this easy. Jason sent a group message between him, Shae, and Me. Before I ever even opened the message, it said it was between Jason, Shae, Tyler, and me. I assumed Jason inadvertently added Tyler to the message because of the conversation (the discussion wouldn’t have involved Tyler). Jason sent me a screenshot that showed I added Tyler at the time I opened the message. Tyler never got the message from Jason but DID get my replies as part of the group message.

its clear that my phone added Tyler, but he was added before I ever even opened the message.