nah akainu was just shocked that another yonko came outta nowhere , i doubt oda had plans for advanced coc that early in the story , i mean yeah he prob thought it as a concept for later on but not these affects . we are shown that characters can fume from their mouth like coc by being scared, imo it was coby being scared of akainu .
It's because Oda didn't have plans for AdvCoC at that point.
What Oda does most likely is going back and reread plot points or any other thing which he needs and based on that, he does the new stuff.
For example, Akainu and Aokiji opening holes in their bodies and evading Haki attacks. This was used to make Katakuri's Future Sight, clear as the day.
Even if the world would collapse, I don't see the guys like Akainu being shocked or flustered, or whatever.
And no, Coby was knocked out 100% by Conqueror's. That's how the scenes with Conqueror's are in manga (in anime ppl knocked out by it don't have foam out of their mouth, censored).