At a glance, it sounds like it doesn't creates energy tension, so much as being something you do with your excess Energy when you haven't been on top of Spawning Larvae

.
I mean in an ideal situation, assuming you've been on top of your Spawn Larvae macro, you should have enough Larvae lying around to react to an imminent threat.
Also, Accelerated Mutation can be used for long-term gain, if you use it instead of Spawn Larvae to produce Drones with, since those Drones come out 50% faster. If it's four Larvae like with Spawn Larvae, then all the better

. It doesn't really matter that they'll only have 50% hp since they won't really be doing any fighting.
Also, if I need to make units in a hurry, and press 's' to select all my Larvae, it's going to be a real pain to need to be careful which units I make with Accelerated Mutation because I'd rather I have Drones spawning with 50% HP than Ultralisks :[.