The funniest thing about this theory is how dumb it makes Noel look
If we imagine that Noel did learn ukrainian just to woo Misha (which i don't believe but ok) why just not speak directly to him in ukrainian? This would literally make Noel Misha's top person in the whole Uranium. Because Misha was forced to move, he can't assimilate and he misses his homecountry. To have someone to talk to in his mother tongue and share culture would create such a strong bond. And Misha would acknowledge all the effort Noel put into it
And pretending to be someone from Ukraine is literally counterproductive for Noel. Having a romance with someone there would only make Misha want to move back more. And therefore leave Canada and Noel behind.
How would this reveal even play out in the end? I doubt Noel also planned to move to Ukraine, our sort of tragedy isn't glamorous enough for him. Did he plan to lead Misha on and then randomly announce that it all was a lie? How would this not make Misha hate him?
At best it makes Noel look stupid. Or like a pathetic guy that is afraid to talk to his crush directly and so creates elaborated traps
but i don't think Noel would even learn ukrainian because i feel he's too self-centered for this