When Miyoshi was imagining a future where Nao remains a guy and they'll show each other their children... he was fantasizing too much may be haha.
Male!Nao is unlikely to marry because he was secretly looking down on females. He used to think all females are cheaters like Nao's mum.
And Miyoshi has difficulties being close to girls.
It's like those two are soulmates and that's why Nao was chosen to 'emerge' haha. That's my own preference XD
Also, in an earlier chapter, didn't Miyoshi tell Nao that even if Nao returned to being a guy, Miyoshi would still love Nao? A bit retcon?