Yes ,they didn't put all tickets in every block on sale ,but most of them were available ,I'd say 90% of the venue when I checked yesterday motrning.
It depends on the venue ,different venues allocate different amounts to the presales.
I find Eventim good in that they let you see whats available and they allocate a large percentage .
The O2 are notorious for this ,they always hold back tickets and release them a few weeks ahead of the event.
Thats why there are so many speculative ticket listings for that venue on resale sites ,the touts know they will pick them up closer to the event.
You will almost always pick up tickets for a gig there the week of the gig on Axs .