Five is the only one not blocked.
Forget about the problem, I'm impressed that they show a Chemex pot to demonstrate!
We are on our third Chemex pot in 45 years. Two broke in very unusual ways, so they are very durable.
My work-around for the filters is to double-up the 12 cup Brew Rite filters, fold and pre-wet accordingly. Seems to emulate the Chemex filtration flow rate.