But that 'clear boundary' thing is a naive bollocks! No such thing!
Both domain experts need to understand things beyond this imaginary and when precisely drawn then highly arbitrary boundary that is more like a gradient than a line normally (also not something relevant in a final good product).
Teams consisting members unwilling to wander into foreign territory and expecting to be fed and deliver over a strict boundary will do horrible things!
(we are not even trained this way btw., professions have quite a bit of overlap and we learn matters others are expected to take care of in practice, and in case of sofware engineering - apart from the most notorious ignorants no one wants to work with - it is pratically impossible avoiding to learn a big chunk of a foreign profession on the fly for delivering a good product, heavy science is no exception!)