It took me a little while to realize why the case with Yamato and Momo ended up the way it did, and the conclusion I've come to is that Momo is being built up to eventually challenge Yamato to prove to her that he is capable of defending Wano on his own and further encourage Yamato to sail out not only to embrace her freedom at sea to the fullest, but to also accomplish her greater purpose of finding the answer as to why Wano should be opened, likely by going to Laugh Tale.
After Momo read the journal and realized the last page was missing, it left him concerned as to why his dad Oden would want to open Wano in the first place and then decided not to open Wano after that. So it's probably not that Momo is concerned about *if* he's able to open the borders, but *why* he should open the borders, and him wanting to surpass Oden would lead to him working hard on his bolo breath aiming and arnament haki usage, presumably trained by Hyogoro, in such a way so as to ultimately become a reliable enough defender. Maybe he'd even challenge Yamato to a fight after finding out she lied to him about why she stayed in order to prove to her once and for all that he has become reliable despite his past failure with the admiral. Would make for a nice parallel too in that just as Momo tried fighting Kaido to get him to leave due to him taking peoples' freedoms, he'd then fight his daughter Yamato to get her to leave due to him wanting his friend to live out her freedom at sea to the fullest.
I admit I'm not the biggest fan of how Oda had all this play out, but assuming he's doing all this for Yamato and Momo's benefit, as well as our benefit of not having our time wasted with Yamato's sailing narrative pushed as much as it was after all, then I think it would make the most sense in that case.
After Momo read the journal and realized the last page was missing, it left him concerned as to why his dad Oden would want to open Wano in the first place and then decided not to open Wano after that. So it's probably not that Momo is concerned about *if* he's able to open the borders, but *why* he should open the borders, and him wanting to surpass Oden would lead to him working hard on his bolo breath aiming and arnament haki usage, presumably trained by Hyogoro, in such a way so as to ultimately become a reliable enough defender. Maybe he'd even challenge Yamato to a fight after finding out she lied to him about why she stayed in order to prove to her once and for all that he has become reliable despite his past failure with the admiral. Would make for a nice parallel too in that just as Momo tried fighting Kaido to get him to leave due to him taking peoples' freedoms, he'd then fight his daughter Yamato to get her to leave due to him wanting his friend to live out her freedom at sea to the fullest.
I admit I'm not the biggest fan of how Oda had all this play out, but assuming he's doing all this for Yamato and Momo's benefit, as well as our benefit of not having our time wasted with Yamato's sailing narrative pushed as much as it was after all, then I think it would make the most sense in that case.