> It really comes down to where you want to create the split: in code or on the org chart?
Deciding on the architecture of an application based on the org chart is probably not a good idea.
And yet Conway's Law still holds up surprisingly well
One way or another, your app reflects the org chart. So either you force the split because of your architectural choice or it happens because of your org structure
One way or another it will happen
While I state later that true decoupling isn't technically possible, it really only makes sense (to me) to attempt it when you've got larger teams split down these lines.
It really comes down to where you want to create the split: in code or on the org chart?
If you've created the split in one place, it will of necessity happen in the other.
If you can avoid the split altogether, then an SPA probably doesn't ever make sense.