This is how it work with Balancer strategy (the one in the screenshot), it take the total token in the pool and divide among the pool token holders. With Balancer pool there isn’t this concern about double spend because the tokens counted are in the pool.
Aave created a space on Snapshot to enable both LEND and aLEND but it just use the basic strategies to take balanceOf these 2 ERC20 and doesnt take burrowed LEND into account see here: https://github.com/bonustrack/snapshot-spaces/blob/master/spaces/aave/index.json#L11-L28
If you want to remove the tokens that have been burrowed to avoid double voting you will need to create a custom “Aave” strategy for it. I can help if someone want to contribute to this.