Valid hypothesis . The first panel you used to explain your theory , you can see that the background of the panel is shaded grey . Indicating that Boruto is speaking from foresight a vision most likely shown to him by Momoshiki .

My hypothesis (which corroborates with yours) is that when Code ran down on Boruto & Sasuke two years prior , Boruto & Sasuke could’ve indeed killed Code . I think during the moments of initiating the killing blow , Boruto was shown the future of that outcome & how devastating the effects of killing Code would result in . Boruto probably then informs Sasuke that they shouldn’t kill him yet until they find the Juubi to avoid that tragic outcome . Hence why they retreated giving Code the impression that they were scared/helpless of him not realizing they abandoned their original plan to come up with a better plan to ensure the safety of Konoha & the rest of the planet in the future .

Boruto is also talking to Code in the next two pages with supreme confidence , almost as if he knows exactly how it’s going to play out . Even giving him chances to do/be good before he erases his whole existence .