Yes, that is how it works. However, that is now how it SHOULD work. There is a difference between understanding why something working how it does, and it being a bug.
You may be able t make sense from that, however, does it actually follow the games logic? No.
Yes, it works, how should it works. Another example is quintessence a darkness creature. It mean this creature is no longer targetable by effects, except from shields and cloak. But Nightfall/Eclipse is still working.
Eclipse have some special working path. It works to all creatures, if there death or darkness, if they targetable or not.
You burrowed a antimatter creature that is affect by Eclipse. This can only to Pest happened.
Unborrowed = -2/5 creature
Burrowed:Part one = -2/4 ; for this moment Eclipse doesn't work, the system checks only the stats, and this mean: it interprets -2 as stable through anitmatter
Part two = 0/5 ; now the Eclipse works -2+2=0
Part three = 0/5 , only now works the effect of halving and the half of -2+2=0 is 0
Unborrowed:- 0/4 ; the creature stats are reseted to the half of the normal normal card atk stat (Pest, 0/4)
- now all effects are counting
- other buffs like blessing and so on (no buffs, 0/4)
- if atk is odd, is rounded down to next straight number (0 isn't odd, 0/4)
- the atk is now doublet (0*2=0, =/4)
- Eclipse works last, because of its special character (2/5)
- now antimatter works, the antimatter stat, wasn't forget by the system, it just work after Eclipse (-2/5)
Oh man, this very complicated ??? But I think this it how it should work.
One comment: When the atk, in the last picture is -1 I'm totally wrong and forget what I wrote! Ok, on the pics Nightfall is working, and I wrote about Eclipse. My comment fault, but for Nightfall it is the same procedure.