Riot seems to create new champion lore from a different standpoint
I've noticed that more recent champions/updates tend to be more about what a character is currently doing or what their goal is in the universe as of right now. This is opposed to telling a character's backstory and then later writing their new adventures or goals based on including them.
Good example - Sylas We know nothing about everything before he was in jail, but we know how he broke out and what he is currently doing. This gives so much freedom for Riot to explore his character in all sorts of different ways. Since there is so much missing from his character, this imprisonment could easily be at the end or beginning of an entire arc (or both).
Neeko, Swain, Ashe, and Tryndamere's updated bios all have parts of their story unexplained which leaves a lot of exploration for their characters in the future. This is a big improvement from old lore, which restricted a lot of growth and is pretty cool.