The space saving doesn't come from the space required to park the cars, but what he's saying is that the roadway accessing the spaces can be narrower ( basically not much more than one car width).
In terms of access, especially for big events, it actually makes life easier - you basically have one Header road with multiple roads going off it. When you arrive attendants fill up one road from the far end and when its full direct cars to the next one in line. Because spaces are at an angle it is faster to fill up compared to turning in at 90 degrees.
A theme park close to me does exactly this and I'm pretty sure they've experimented on how to pack the punters into as small a space as possible...
Better if, like my example, you drive cars in one after another. At least one car can exit forward (much safer) and can deal with the over sized truck / suburban issue. If you look closely you can see how the access road is pretty narrow (basically not much more than one car wide - I know I've drive in enough times). Saves on the amount of tarmac used as well - parking areas is gravel.
All in all it can work I think for car parks where loads of people arrive, stay for a long period (like them park, car park for an office etc), but wouldn't work so well for something like a supermarket where cars are coming and going all the time and where a lot of them would need to reverse out of the spot leading to many more scrapes and fender benders.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
