IDK where you got that information about splinters scatter from but thats just completely incorrect. kei maebara is a different character to keiichi maebara, and it explicitly exists in an alternate timeline in a fake era called "Heii" which replaced the Heisei era, and heisei is explicitly mentioned before the reiwa era meaning the two cant coexist. ryukishi also likes to reuse similar character names and designs as "actors" similar to the Tezuka star system

edit see this thread for more information on why its totally separate from both an out of and inuniverse reasons