That Sasuke needed 4 dead historical figures to hammer the point Itachi made many chapters ago reflects poorly on his character regardless of how you choose to interpret the latest flashback.
When the massacre happened, Sasuke experienced the aftermath, but did not understand the context behind it. This is fine and natural in fiction and his rage is mostly justified. After his showdown with Itachi, Sasuke received all the context and background he needed to make the right decision.
He didn't.
It wasn't until much later that he received ANOTHER history lesson on events much more distant from him that he realized "Oh shit maybe my dead brother had a point!"
This reads one of a few ways:
A) Sasuke resonated more strongly with the Hokage's stories than his brother's stories, which makes no sense whatsoever and is just bad writing.
B) Sasuke needed not only Itachi's backstory, but the backstory of the entire history of the ninja villages before coming to the conclusion that we were all expecting but didn't see until now. This interpretation casts him as an extremely dense and stupid individual, which is hypocritical considering this is a world where everyone grows up far faster than they should (and Sasuke had no shortage of childhood tragedy to kickstart that mental development).
C) Kishimoto wanted to insert the entire backstory somehow and resolve Sasuke's angst, using this time to nail two birds with one stone. This is just extremely lazy.