Why would that happen?

I work in a reinforcement learning context using the stable-baselines3 library. If I log 20 scalars every 2000 training steps and train for 1 million steps (which is not that big an experiment), that's already 10k API calls. If I run 10 of these experiments simultaneous (which is also not that many), that's already 100k API calls based on the explicitly logged scalars. Implicitly logged things (hardware temperature, captured streams) may come on top of that.

The logging is already batched (meaning 1API for a bunch of stuff)
Could it be lots of console lines?

That's good to know. I don't think its console lines alone, as described above.

BTW you can set the flush period to 30 sec, which would automatically collectt and batch API calls

Oh nice! Is that for all logged values? How will that count against the API call budget?