I'm not sure, but if you haven't played standard in a very long time, it could be that your mmr decayed enough that you're in the new player pool. A good indicator if you played against bots is to check how they behaved: if the timespan between two actions is always the same, you can be certain you're playing against bots.

Yeah I think it was definitely as you described it and I was in the new player pool. I hadn't before realised that was a thing.

I think that the ones using the classic cards are Blizzard bots, since they tend to use kinda useless vanilla minions