@ToKyo PewPew, to explain my point a little further:
1) Counter hit 3P.P+K - P6P.P+K - 3P.P+K -
4K.P+K - Chifu K.P+K - Tenfu P - PPK
2) KK - 3P.P+K - 1PP.P+K -
Chifu K.P+K - Tenfu P - PKKK
Notice how both combos have different launchers (underlined and bold). The first combo has 4K.P+K as a launcher and in this combo Chifu K.P+K is a JUGGLE instead of launcher.
Now compare it to the second combo. Here the launcher is Chifu K.P+K. It is used to launch the opponent into the air.
My point here is that if Chifu K.P+K is used as a launcher, you can follow-up with Tenfu P AND end with PKKK.
Whereas if 4K.P+K is used as a launcher, and Chifu K.P+K as a juggle follow-up, and then Tenfu P, then you can NOT use PKK as a combo ender.
Long story short:
Chifu K.P+K launcher = PKKK allowed (no wall)
Chifu K.P+K juggle = PKKK not allowed (no wall)
Now you could be asking,
WHY does PKKK whiff if Chifu K.P+K is used as a juggle? This could be because in the first combo, you ALREADY have 2 juggles (Chifu K.P+K and Tenfu P) so the threshold of combo can be overridden and does not allow 6 hits (like in PKKK) but only allows 5 hits (like in PPK). Whereas in the second combo Chifu K.P+K is your launcher and you ONLY have 1 juggle (Tenfu P), therefore there is more space for more hits and allows for 6 hits (like PKKK).
Hopefully you understand it now.