That's absolutely busted, pretty sure you just got insanely lucky there rather than it being a bug. Humans tend to view randomness differently from how machines view it 😉
Since there are 128 collectible War cards that can be spawned, my napkin math says that the probability of this happening is 4C3 * 127 / 128^4 = 0.0002% or thereabouts. Not too sure whether it's entirely correct but either way this is pretty close to winning the lottery in GU 😂
Ty for running the numbers! I was very curious about this.