Various 4-stroke engines have used similar, but metal, keepers on valve springs for ages. They were always split in two pieces. I don’t see any reason the plastic doo-dad on a shift rod wouldn’t work just as well.
I don’t think the split keeper will cause any problems….Those plastic keepers are a royal PIA for sure…. One word of caution though…Be sure that lower shift rod is threaded all the way into the gearcase or the shift adjustment will be way off. Sometimes, we inadvertently “unthread” the lower shift rod while disconnecting/reconnecting the shift rod connector….