I can see the argument both ways. Pulling out altogether might be a slight overreaction (based on what we know anyway) but being misled like that is not exactly great.
Mmmm yeah, being offered a headlining spot and then just flat out finding out it was not the case would sour any deal with any band as big as them. It also doesn’t help that the band they’re being replaced with is Sum 41.
It’s a 3 day festival, Architects was still the headliner of their day. Parkway Drive was one day (and the name ahead of them on the poster, Architects the next day, and Sum 41 the last day.