Those spoilers were fake why would Ichigo use Blut?
but Ichigo blocks the attack with his blut(?), he then uses Getsuga Tenshou
No, the spoilers aren't fake (...yes, they may be, but we don't know yet). And there wasn't said he used Blut.
There is a freaking "?" in the spoiler which almost everyone is ignoring. The spoiler person doesn't know what the hell Ichigo used to block Yhwach's attack.
I would say that his Fullbring evolved into some sort of Quincy power, except he isn't supposed to have that anymore...
This is classic Kubo, it's all I can say. I can't believe so many people actually called it.
Or perhaps the quincy power is just another type of fullbring power.
Still not sure why Ichigo would have to be a Quincy to use Blut, when it appears not a standard Quincy ability but something granted to them.