Yes, it's immediately available for someone else to book. I followed the instructions of the person who had done it before me successfully and it worked both times.
You coordinate a time that you're both logged in, ie. 12:15pm. You're on the restaurant's reservation page with the date, number of guests, etc filled out in the fields. They drop their reservation at the exact moment the clock strikes 12:15pm. You hit refresh at the same time, and keep refreshing until it pops up. Both times it happened within about 15 - 20 seconds for me. It was fast. Immediately grab it and you should be good. I highly suggest you pick a time that less people will be cruising the internet. Weekday mid morning when most people are working is good.
OMG....I just remembered a website another person referred me to and it worked for my first BOG reservation. It's a reservation finder on the Touring Plans website.
https://touringplans.com/walt-disney-world/reservation-finder
I actually subscribed to this website back in March. I'm not sure if you need a subscription to use the finder or not. I use the website a lot. I even used it to request a room at my hotel. It has a layout of every hotel, with room numbers and views from the windows in each specific room.
I set it up to receive a text when the restaurant I wanted had a cancellation during the time of day I want. The website says it's still in the "testing" phase but it worked for me. When I got the text about BOG I immediately went onto the disney website and it was there. Twice I've received texts about cancellations that were times that didn't work for me so I didn't pick them up. If that happens, you have to go back in and renew your request. I didn't realize that at first. The system tells itself it has fulfilled your request and stops the search.