As people pointed out on Discord, it's definitely possible that if the RNG generator used to generate AI trainers is comparable to the one used to generate wild pokemon and gifts, so possibly based on date, hour, player ID, or frames, or similar things, it does not surprise that occasionally there could be "repeats" of similar sets in short terms.
In fact several of us reported that not-too-rarely you could run in the same trainer or trainer archetype 2-3 times over 10 matches for example . However, even in such situations, it wasn't generally "A archetype that counters", rather, the same archetype, which generated both edges of super easy matches or relatively hard.
Unfortunately, there'd be no realistic way to prove if the RNG generation is indeed linked to fixed numbers, possibly even manipulable in same way as RNGing Pokemon, without actually hacking the game, but it is definitely a possibility nontheless.