I don't claim to understand the workings of talent pools, but presumably they kept at a certain level, say 20 individuals. If a TOC/FOC plan to take 3 people from the pool then it's likely that's going to coincide with a recruitment campaign go find 3 new people to go in to the pool.
So, following that logic, if you're in the middle of the pool and you're worried they're recruiting again and you've been overlooked, there's a good chance it's because that someone above you has got a start so you've moved up the list.
Of course, this is conjecture, so I'm happy to be corrected by anyone with better information