Well that seems to make sense, but then Data took over Lore via his memories, right? So it seems like if you have all of someone's memories you become that person?
More their experiences. Experiences change people and this gets wonderfully hazy when its robots basically copying memories and experiencing themselves. Androids dreaming of Electric Sheep n all that.
Data exploited the fact he knew Lore would keep them as Trophies to look at and crow to the crew about when Lore Took over.
Lore also outright states that he keeps them in his own memories as a measure of his own worth. His achievements, accomplishments etc. Data meanwhile, was given love, friendship, companionship and so has treasured memories which he freely gives to Lore knowing what his brother would do.
The experiences and memories change Lore completely, he incorporates them willingly initially to boast about to Data's friends to use against them. He understands now, and the end result is a new personality.
End result is someone new, but with the old Data at the core.
I actually wonder if Data really is Data, we saw the old one vanish willingly, and then the Lore personality also vanish, replaced with another Data-core inspired entity.
B4 parts was probably still struggling to sing Blue Skies and just went with whatever happened.