Valid, though I expect this being down the block from the festival theatre, it probably was being actively patrolled. I was a bit shaken by a prominent sign threatening a $400 fine for illegal parking, though having just checked the website for the City of Stratford, it looks like the standard municipal parking ticket is $40 if paid promptly, so the $400 fine was probably specific to parking in the theatre's dropoff zone or fire access or something.

All that say, I think you're probably right... next time instead of using my phone to install and sign up for a parking app, I'll just use it to check what the fine is and wipe hands on pants.