The tank is NOT pressurized as it has a vent that goes up on the roof. So, not to worry.
The only problem with closing the drain while using the rinse at the same time is that if for some reason you get distracted and forget that the rinse is still on.... you will have a surprise coming as when the tank gets full, it will force water up the toilet and out on your floor. Don't ask me how I know this.
What I do is I have attached a quick disconnect on my black tank rinse hose at the faucet and I keep my iPhone in my pocket with a 3 minute timer/alarm. When the alarm goes off, I turn off the water to the hose and REMOVE it from the faucet.
So to answer your question.... yes, you can use the rinse to put water back into your black tank.
Ron