There’s only incentive to do that if the mempool is empty. If the mempool is full, there will be plenty of transactions for both the first miner and the next miner.

In fact, this entire paper only makes sense if the mempool is near empty. If the mempool is full, then there is no reason to mine an empty block because there will always be transactions left for future miners.

So basically:

• Mempool full = miner would mine full blocks just like intended.
• Mempool empty = miner would mine empty blocks but that isn’t a problem because there are no transactions to process in the mempool.