You're saying that like he can do that in literally ANY scenario, despite the lack of knowledge in such topics and dealing with supernatural forces. Toriel & Asoge have lived for millenia alongside humans and had a human child in their care for long enough to remember their unique quirks like filling cups "the most efficient way", yet they are only aware of the possibility of time travel after witnessing (and being told) by the 6 human souls that fell into the underground before Frisk. Asriel himself was also unaware until they became a flower.
You could maybe argue he could this because Sans could, but that guy has actual scientific knowledge on timelines, can read expressions to count how many times a human has died/if the human has killed him and could actually get close to the duo without risking instant death (+ he's
at least Genius and more likely to be
extraoadinary compared to Johan's simple Genius rating)
Once again, this wouldn't significantly effect Clover and
CERTAINLY not Flowey.
Clover has literally been told that they've died a hundred times by Flowey AFTER dying to Flowey and they still refused to submit and give up their SOUL. They've resisted until Flowey gave up and reset because he realized Clover was "too determined" and that was when they were just LV 1 with a single kill (the only requirement to get to Neutral) and Geno Clover has enough determination to surpass Flowey's SAVE & LOAD, meaning if Johan even got the duo to fight eachother that'd mean he'd still have to deal Clover who can get pretty violent at pretty much anything that gets in his way, is immensely strong and is unlikely to want anything get near their face.
Flowey has reset the world and done ever possible thing that he reduced it to just "sets of numbers" and "lines of dialogue" with the only obstacle he couldn't get by with his knowledge being Asgore, in fact that's the only monster he couldn't get past because otherwise he'd have the human SOULs already. Flowey could get past Sans eventually and only found his brother Papyrus the most entertaining, with him stating that it took very long for him to get bored of Papyrus. The only instance of Flowey "giving up" is at the end of both game's geno route, where he pleads with Chara (who he realized would kill him if he got in the way) and where he mocks Clover by saying the underground will be their grave before dying, both instances involve him losing the power to SAVE & LOAD which Johan doesn't have.
Flowey literally has the psychology of a Player, if Johan tries to SI him he's more likely to get his or someone's SOUL snatched alongside Clover's like in any neutral ending or the beginning of UNDERTALE.
Retaining memory is more of an advantage for both of them, since they're going to learn how Johan behaves through trial and error. Either that, or they just brute force through everything out of frustration, they are both above 8-C by a significant margin and Flowey has a significant range advantage with his vines after all.
Flowey has, his name is Sans the Skeleton. This also acts as an answer to the reset thing,
cause Flowey does that if Sans knows anything about him. If Sans and Johan actually have comparable psychological wit in your mind, Flowey would reset if given the chance and Clover has (somehow) been taken out.
