pretty much in my experience -they will tell you and confirm based on babies measurements +/- a week/few days. They did this with me.
They might not actually say the EDD but what age the baby is ... like you are e.g. 7weeks 2 days.

They go by growth charts in millimeters/ measuring sac etc.
It will most likely be an internal scan too if you are under 12 weeks.
goodluck.