With regard to kill two, then devour another:
In his original iteration released on PC/Mobile in the Adobe Air client, there was a concept I am going to refer to as “target lock”, where a spell with multiple components intended to affect the same target would select the targets once, and all effects would be applied in order to these targets. Kraken was one such troop in his original release - he targeted the last two troops, dealt damage, and has a chance to devour the “last troop”, meaning the last troop when the spell was initiated, meaning it if died, you wouldn’t get another devour. Target lock does not exist on Unity, therefore, all multi component spells have issues with their subsequent components “leaking” onto other troops (ie., Khorvash, Pride Hunter, and yes, Kraken).
I’ve seen people argue back and forth as to whether or not this was “intended” and citing the spells wording that it is supposed to work this way, but the fact remains that the current behavior is most likely a consequence of the engine switch. I highly doubt the devs singled out Kraken’s spell and said “Kraken isn’t good enough with the version we pushed through QA on our Adobe Air client where we designed him even though it has both board mod, damage two targets, and a chance to devour. Lets make Kraken’s spell better and more accurately fit the description by allowing it to simultaneously kill two enemies and devour an untouched enemy. Since Unity doesn’t have target lock any of the multi-component spells, just porting it over with the current targeting scheme will make it do that, but this is an intended and informed change we made that just happens to coincide with bringing the troop to Unity. Also, lets make it always work this way on Console, but PC/Mobile has to wait for this change until they get Unity, even though we could easily separate the spell components on Adobe Air since we already have other multi-component spells that don’t target lock”. A more accurate representation would probably be “oh, I guess it works that way now. I hope people don’t notice or it doesn’t break anything major, because that means time and resources that have to go into fixing it”.
Whether or not it will ever be “fixed” and whether it needs to be fixed are two different things that can be argued on their own merits, but I really don’t see how Kraken got to where it is now either by “always being that way” or by intentional adjustments to match spell text when spell text is much easier to change.
In short, yeah, it is probably a bug. And yeah, it is probably also “working as intended”.