It's not really that part that bother me the most rather than everything Oda has to made for this twist to happen.
- The samourai not telling the strawhat their reason to go to Zou. Kinemon is when since Punk hazard but when he is about to tell them, a monkey conveniently fall from the sky and separate conveniently the 2 samourais from the rest (I remind that the trip took all day…)
The samurai had no reason to tell them, and until getting to Zou the Straw Hats were having their own stuff to deal with. As with convenient, there have been a lot of conveniences in this manga. Luffy getting rehydrated with the barrel of water falling on top of him, being the one person on Skypeia being able to hit Enel, Kuma being there to save the Straw Hats on Saobody, Moriah getting the final blow right before the sun comes out, etc. etc.
If you don't like the other conveniences, I have to question how you can handle this series where convenience is the name of the game. If you can handle the other ones, why is this convenience too much for you?
- Momo hiding in his room for no reason apparently and conveniently going out of it a the good time
Pretty sure Momo hid because he also thought the minks would not like to see a samurai. He seems to change on a whim with his forms, so hiding so no one finds out. It was convenient that they met up, but this Manga, for better or worse, has done that before.
- 3 strawhats conveniently falling asleep
More of a gag, which was hit or miss for people. I liked it just to see the older and more "mature" members get a silly fail
- The strawhat deciding to lie about the samourais despite knowing it would be an issue
They just went through hell and their assumption was that it would cause emotional stress. The last thing they needed to do at the time was mention the samurai, because everyone was still recovering physically and emotionally. It's not like the minks asked about the samurai to them but just stayed silent on the matter.
- 2 samourais deciding to talk to Bariete at the top of the cliff when they have spent one complete day together (they must have talk about Kanjurou artistic style in between). Him running away crying rather than stay with them
Another thing One Piece has done before is characters not always being logical. Some cases it works other times it doesn't. I can see the problem with this one but because I personally felt everything was effective overall it was ok.
- I also find Kinemon attitude at the end rather illogic
I find the idea that they thought minks were unfriendly before knowing this stuff to be more illogical. In this case Kinemon knew the history and just asked knowing that the minks respected the family.
And I probably forget some others.
Like with Jabberwok, it comes down to personal opinion and interpretation. The only thing I'll say is that complaining about convenience in this manga is silly. Many things, from major to minor in this series have been convenient that I've seen people not able to read the series because of it. You don't have to like this scene, but I feel the arguments you are making are silly.