That's true if you're going to try and kill him with bullets, but if you have your melee weapon out (you can get it out in no time), then it takes just one chop to finish the job. Same goes for Hunter. Get the dead-stop and then get the slash.
It's a more viable defensive tactic than melee spam, because for the Survivor it saves time, and energy they could use defending against other targets. Plus from the perspective of the Special Infected, it's just more dignified.