There seems to be a t3 gunpuppy in this mission. I've seen it once before on my other account, but didn't manage to get a screenshot of it. I take it that since this is meant to be a t2 mission, this is probably a bug... It acted like a t3 gunpuppy too (5 staggered bullets, pure elemental damage, much higher health than the other gunpuppies next to it).
Decon zones in general may spawn a higher tier turret, not just in these mission.
I'd say it's intended, not a bug. Like teh alphas of wolver dens, etc.