That sounds like a more plausible concept. I've seen that be the case with Lucina's dolphin slash in cruel smash, occasionally it would trip the opponent, because as you said it would be due to the weak knockback.
So to put it in a better perspective I think the best option all Roy mains have when attacking someone on a platform is u-smash OoS, up-b OoS and falling uairs and nairs. Shielding helps cover possible platform drops and shield drops your opponent might attempt (albeit shield dropping is hard as hell through platforms, I don't see anybody do it consistently in tournaments.)
But from the video you provide it looks like you can get some solid follow-ups, you can attack off of a trip right?