Traffic restrictions are not part of the "15 minute city" initiatives. I think they are often confused because of Oxford's traffic filter scheme. As the article

Traffic restrictions are not part of the "15 minute city" initiatives. I think they are often confused because of Oxford's traffic filter scheme. As the article you link says, tying walkable city initiatives to one particular city's traffic scheme is indeed a conspiracy theory. If you have valid criticisms of the traffic filter trial in Oxford then that's fair enough, although I imagine Oxonians won't be particularly interested in hearing it unless you're a local resident.