Illogical bcuz Obito said Susano'o was a rare ability among MS users yet all active Uchiha in Naruto have one and an Obito dying and coming back to give Kakashi a power up temporarily is just as much an a$$pull as Rin helping Obito and Kakashi when she is dead. :|
A$$pull is something u pull out your butt for the sake of plot. Temporary or permanent Kakashi getting Obito powers was an a$$pull because it was a rather forced method of making Kakashi useful
No asspull is a fan-made term for butthurt fans to describe plot events they don't like, and put them into negative connotation.
What happened makes sense when you look and pay attention to the nature of chakra; it was meant to connect people and has power to enter the physical world from the spiritual one, this whole concept is explained prior to the event. It's just outlandish and people are mad kakashi used perfect susanoo but obito didn't, so they try to make the scene look bad.
But perfect Susanoo on the first try... Is pushing credibility. It's not a plot hole, but it defiantly comes close to one.