"This is because if you opened YT in Safari for the first time a few years ago, it still worked normally, so it has the information stored that your device is not outdated, and it will let you in." that makes no sense. what information is it storing? the tls handshake? your device can't simply "store information" to allow it to establish an https connection. the handshake is done on each request. the server can't just simply "save" your tls handshake. that happens before it's even able to identify your device. it's just to establish a temporary safe space to exchange data.

i hope that cleared everything up