Maybe for like 0.5% of the climb they could do that, if Alex was close and he could somehow get a harness on, they could help him.

If he got injured it's not like he could step left and there is a magical video game ledge that appears, It's all or nothing.

Its a multi pitch route. There are multiple ledges that can be comfortably sat on. Assuming the injury isn't to catastrophic he could make it to one of those points and be rescued.

That being said anyone trying to claim the climb isn't "pure" enough it mental.

Somewhat related: http://semi-rad.com/2017/05/but-did-you-really-climb-it/