He was arrested for disorderly conduct. The only conduct he was conducting according to his account was filming the police, so it seems clear that filming the police was the disorderly conduct for which he was arrested.

Filming the police isn't (or shouldn't be) illegal in the US, but catch-all laws which are enforced at police discretion make it de facto illegal where police decide it is.

I think of you're accusing him of making up a different scenario here, you'd need to have some evidence which wasn't presented.