It is not the end of the world if you get antifreeze into the hot water tank. It will flush from there just as it will from the lines.
From memory of our 210, there are three valves near the top of the tank, under the kitchen sink. When the middle (bypass) valve is closed (handle perpendicular to the water line, and the other two valves are open, handles parallel to the water lines, water will flow into and out of your water heater.
For ours, if the bypass valve is closed when flushing the lines (and the other two valves are open), it will flush through the hot tank. Just the opposite of what you said from youtube.
To bypass the water heater, put the valves in the opposite position as stated above. Water will then bypass the hot tank. This is what is normal to put antifreeze into the lines and not the tank.
I suggest flushing out antifreeze with the valves in the same position they were in when antifreeze was added. that way flush water will flow the same places the antifreeze flowed
I will look at ours tomorrow and will post again if the above is incorrect, or incomplete.