what you call leapfrogging is also known as making progress.
Looks to me like a pretty open road with good visibility.
It looks like a wide country lane with decent width carriageways and a dashed central line- I would expect this to be a national limit.
If this sort of maneuver was beyond acceptable limits, there would be a solid white line and/or a 50 limit.
finally, given the car is a dacia sandero and it overtook you with aplomb - chances are your Father was driving too slowly/over cautiously.
Guy drives an Audi, a performanced Audi, and never seen him floor it. Fam, speed up, the road is a 30mph, do 30mph, stop sitting at 20mph. One time, I was at a traffic light in my Corsa, I was expecting him to do a launch, the guy waited like 4 seconds before moving. WTF????
This guy is the best driver I've seen in my life , I was late to a meeting one evening and he offered to give me a lift in some miserable weather, and the driving was excellent.
Parks wherever the fuck they like causing others to be blocked in. I'll key your paintwork next time.