I used to think that was the case, but then i think i read somewhere that it only recovers 20% of the kinetic energy. Can't find it anymore though

Maybe you're thinking of the total range boost provided by regen braking? That's often shown to be roughly 20% via studies;

https://sci-hub.se/10.1109/vppc.2011.6043109

> Simulations show that the energy reduction of the vehicles under test can be more than 20% by applying regenerative braking.

It's an older study, but they show the regen efficiency at 60% for the EcoTruck and 70% for the bus.

There is all the time friction of air and the road. You can never recover that.

And in rare cases where you actually can recover energy, at non emergency slowing down, it is probably indeed in that ballpark, wich is something(especially in city with stop and go), but not very high or much. With very high tech, you can increase that number a bit, but not worth the effort. Electric cars need good batteries and every improvement there is good.

The extra weight of a big battery requires a bigger frame to carry it, bigger suspension, wider tires, and so on.

I’m not really happy that some of these monster EVs are approaching 10,000lbs with fast 0-60 times. It’s like a kinetic missile that can reach a momentum capable of obliterating your average 3000lb compact car in under 5 seconds.

It's nice to have a way of recuperating energy but it doesn't solve everything.

So the first person never set goal posts around efficiency, that was an assumption by the second person. The first person could always have meant that the collision risks from heavier vehicles are higher, while the second person misunderstood their meaning. No moving of goalposts here.