1. They might not, but that's not decisive for reproductive isolation. Basically, those two populations have diverged enough that we know, from studying speciation in general, that they are on separate evolutionary trajectories never to join again. That's the decisive factor - they are two distinct branches of the tree of life. That's not the case with any two human populations. Human history shows that we are different from all other animals in this sense: no matter what obstacle – weather geographic or otherwise – separates us from each other, we ultimately find a way to overcome it.

2. You might have picked a bad example with these two species, since they appear to be surprisingly far apart genetically, a lot of their common appearance being explained by convergent evolution not by shared ancestry.

PS: A lot of this stuff is counterintuitive and understandably perplexing, but scientists have worked hard to get to the bottom of things and deserve a bit more credit for it. You base a lot of your arguments on suspicions and gut feeling. I recommend measuring those misgivings against the freely available AI chat apps, it will help you get a grip on both the depth and complexity our scientific understanding of this domain. Ask it for sources, go check those sources, ask deeper question, push back as much as you need. Here's my interaction with Claude on these questions:

https://claude.ai/share/bea11195-731b-4301-a2f5-fb669961a60e