In my opinion, splicing should not be considered cheating as long as you dont cut portions out of the speedrun that otherwise could not be skipped such as cutscenes or entire missions. Splicing would also be better accepted for longer speedruns like GTA V because of people who don't have the time to sit there for 12 hours straight like people in high school and college. It might seem a little weird to have this opinion, but in my opinion, speedrunning is about how quickly a game theoretically could be beaten and is not about showing off your skill. Also on RNG dependent games like GTA V, splicing would be good for that, but it would only work on some games like and not others, and also for it to not be considered cheating, the reviewer should be informed that it is spliced first.