Allows extra pulls? Not sure what you mean, unless you mean the events where the usual chances of getting epic/legendary champions from ancient/void/sacred shards (check the portal info screen) are increased. 

Next Friday, we'll have a 2x on sacreds, meaning the chance to get a legendary from a sacred shard is temporarily doubled from 6 percent to 12 percent (obviously if you only have 1 or 2 sacred shards, you still have pretty low odds to get a legendary). Two weeks after that, we'll probably have the same thing for void shards (or is it ancients? either one, they're on a rotation with one event every two weeks). 

In the weeks inbetween the 2x, there are 10x events, which sounds a lot better, but for new players it really isn't. In 10x events, the chances to pull epic/legendary champions from shards are the same as always, but IF you pull an epic/legendary, there is a 10x higher chance that it's one of the specially selected champions of the event.

 So basically, 10x events are for people who already have most epic/legendary champions and are really only interested in certain specific champions. For people who would be happy with most epic/legendary champions, the 2x is much better. 

As I mentioned I only heard it referenced in passing "I'm saving my shards for the next pull event"... so I assumed it was not only incomplete info, but also questionable in accuracy. 

I HAVE seen the events that increase the CHANCES of a good pull, I appreciate you connecting the dots for me.