Slot issued after startup?
Major European airport. Short domestic flight. We ask for startup at EOBT +13. ATC approves start but asks us to update the flight plan. We ask the company to update our flight plan, and during pushback ATC tells us we now have a CTOT about 1.5 hours later. While trying to coordinate a new parking stand where we can wait, the slot is improved and we take off after about 25 minutes waiting on the apron.
Can a slot be allocated after ATC has approved startup?
Did we get the slot because the company delayed our flight plan?
Is there a valid reason why ATC would ask us to update flight plan after approving startup?