1. The agent said "open seat", not "open suite".
2. On European flights, the "business cabin" has a variable size. Depending on loads, it may be that only the very first row in the cabin is deemed "business". Any row that has a middle seat occupied - even if it is row 2 - means that this is an economy row.
3. On most European shorthaul carriers, staff do not intervene to stop the economy class passengers from disembarking before all business class passengers have left. Business class passengers are seated in the first rows - if they wish to make a swift exit, then I suggest you take the initiative upon yourself to step into the aisle without delay.