Folding pins is a pro/con issue. Personally for this form factor I prefer folding pins as this is a more travel charger and it spends a lot of time next to something in a bag which would appreciate the non-gouging benefit of recessed pins. But folding pin designs are easier to fall out the socket. So I think these are for home probably and then why does size matter for something which doesn't move....
It is pretty clear the designer here was thinking of a global deployment, the non-folding design is a press-on glued simple pin which can be a different press-on pin shape for UK, EU. Folding pin design is pretty much unique to USA or you're talking swappable slide-on-clip type pin which is physically bigger. So in this case they traded global roll-out first over folding.
I've expressed my views that size matters less the smaller the size is, so size matters little in these lower wattage products. Size matters more when we're looking at the 45W, 60W, 100W and if you looked they are huge and where we still need the greatest electronics innovation. So imagine this size and say 45W. That would actually power my laptop.
There USB meter, I want that!