Board Thread:Questions and Answers/@comment-25801533-20150531094407/@comment-4133073-20170702095428

I actually think Byakuya's "It's almost as if..." was referring to the fact Ichigo's Bankai looks and functions just like Isshin's. Byakuya likely knew Isshin personally since they were both captains at the same time, and must have seen his Bankai at least once or twice.

So when he sees Ichigo with a similar Bankai, it's a "Hold on, why does that look so familiar?" moment to him. That coupled with the fact he looks like Kaien was probably really confusing.

...That got me thinking that now that Isshin regained his powers, it means he's stopped aging again (think about it, the Vizard still look the same after 100 years, but Isshin has aged in 20 years - it was because he essentially became human after he lost his powers). I wonder if he ever goes back to Soul Society to see family and friends every now and then...