Even if I love Sanji performance and didn´t see it as L, he was probably knocked out for shorttime similar as Ulti was against Yamato.
When King hit Sanji into the ground, many things happen after the hit with means minutes pass.
-King hit Sanji into the ground, Luffy make a comment
-Luffy tell Yamato to protect Momo
-Big mom attacking Luffy
-Big mom going after Nami with Zeus
-Franky and Brook save Nami via driving and hit Big mom
-Fodders running away because of the anger with Big mom gonna show
-Franky target is Big mom, she make a comment for the Strawhats
-Numbers and Samurai get shown, multiple things happen.
-Franky hit the number with the beam
- Big mom want to attack Franky but Jinbe and Robin came into the game
-Sanji wake up again with minimal bruise thanks to the RS(with he himself call out)
Between Sanji hitting the ground and Sanji standing up again, multiple minutes pass, multiple things happen, King even had enough time to assumble his squad with mean he left the place of Sanji very fast.
I think Sanji was knocked out for at least 1-3min similar as Ulti was after getting hit by Yamato.