It's actually a quite common saying; because the most important factor is minimizing time to treatment. Every second a part of the brain dies. After a few minutes there will be significant permanent brain loss. (according to some sources on average around 2 Million brain cells per minute)

Thats also why STEMO exist. They're special ambulances with a CT and teleradiologocal appliances (meaning the supporting radiologist is not necessarily onboard but joins remote) and medication and specialized stroke-medics. Because a regular ambulance will cost the patient too much time - and to much (living) brain matter