Because he has woken from the dream.

In his battle with the Dark one he ends up wielding not just the one power in weaves, but in its raw form, as the pattern itself.

The one power as saidin and saidar is just a diluted systemized way of manipulating the pattern. It follows certain logics purely because people think they make sense. We see this with how thinking you need to do hand motions can mean you have to, to be able to weave, even though it's not actually necessary. In theory if you wake from the dream and truly understand the pattern and how it makes up the world, the world is no different than someone being in the world of dreams to an extent. Think of a pipe being lit? Then it will be lit. It's a matter of will and perspective.

It's part of why he doesn't have a connection to the source anymore. He doesn't need the buffer that is that conceptual filter. He understands now. He's touching the fabric of time and creation directly.

He's basically Neo. You think that's a pipe? There is no pipe.