To me they are not making more steamlined or easier. Well easier to program . I twitch occasionally reading some the changes. Having only 3 spell lists means you don't have to create another spell table/database with each new class.
New class spell casting arcane table.
It doesn't even seem to me like there should be more than a trivial difference in programming difficulty. I don't know exactly how WotC/Beyond stores this sort of information, but a reference table with spells as rows and classes as columns would only need a single row added for each new spell and a single column added for each new class.
The developers are saving themselves a very small amount of work by taking away their own ability to make interesting decisions on a class by class basis.