The amazing part of Pereira vs Rountree fight was that is has lasted for 4 rounds

With odds like 4.5+, Pereira should have chopped him down in first or second round. But the fight went till 4th round. Only fight against Izzy lasted till 5th round. All other opponents Pereira has finished in first and second rounds. For me this means that Rountree aint that easy opponent. Even though he lost, his value imho has increased. The second round was the best of Rountree. But, starting from third, I felt like Khalils gas tank started to leak heavily. What do you think? Am I the only one to notice that he turned extremely slow?