In the diagram he wrote in "VENT TEE FOR STANDPIPE VENT". A vent tee is a vent tee, it is not the same as a sanitary tee, which appears to be what is actually being pointed to.

Here, we cannot use a tee as a vent take-off, we must use a combo. Some inspectors might let it slide, but all inspectors will accept the combo, so why take the chance.