Note that a large adversary can continue the decoy-flip-flop attack for a long time even without savings.
In the simulation, an adversary who controls larger than 37.5% of the validator set succeeded to delay the convergence for 100 epochs by pivoting only once every epoch.
In an extreme case, 51% attacker can make a permanent liveness failure.
Since these attacks only use the fresh votes from the current epoch, the inactivity leak does not punish the adversary.
The adversary can increase the ratio he controls by bribing other validators to join the decoy-flip-flop attack with their fresh votes. Since the bribed validators are not punished by the inactivity leak, the cost for bribing would be the reward loss + α.