Every single time I’ve shown up later since the “chronically late friend” usually does, is the exact moment he/she shows up right on time which just further proves that they should keep showing up late since I was late too.

Having a conversation with them about it is worth more or when making the plan, you can mention you have something at a later time the same day so there’s more effort to make it on time. I think the chronically late friend just doesn’t realize that there might be something after this event.