After reading the chapter,i feel like denjiro might be the traitor lol,he is too shady and maybe that's why he hasn't yet appeared in the current timeline.At least kaido has clearly stated there is a traitor in oden castle who warned him of oden's attack on the beast pirates.
Regarding kaido vs oden,kaido looked to me a bit better than what the spoilers implied; Yes oden's strength exceeded what kaido thought but the scar kaido received was in dragon form and he probably couldn't dodge it and since oden has great attack power,he made a clean hit through kaido's toughest form.
Now i'm not implying kaido would've won if he started in base form,just that he could've put up a better defense in mobility and counter attack.
Regarding the interruption by the old hag,that was a clear dirty move by the beast pirates even though kaido had nothing to do with it and i'm not sure oden would've beaten kaido even without the interruption. The fight is very similar to luffy vs kaido where he pumelled kaido in dragon form easily with g3 but couldn't put kaido down for good in g4,so i think kaido and oden are on a similar level with kaido having better durability and stamina.
Finally we have seen both enma and ame no habakiri scarring kaido so i expect those who thought enma was a magical sword which enabled oden to scar kaido are finally put to rest.
Oden scarred kaido due to his own power and haki with both swords AND not due to some magic.If a great blade was able to that to kaido,pretty sure a supreme blade (like wb's) and a black blade like yoru and shusui can do the same if in possesion of a great haki user.
Finally,In 2 weeks i expect oden's execution and end of flashback hopefully.
Ps:kaido also implied man power is important in a war when the leaders of both parties are on a similar level so the strawhats and their alliance might have a chance in the upcoming war if a 3rd party arrives to stalemate big mom.