They're taking the basic "ClanDestine have Djinn ancestry" idea and running with just that much. It lets them avoid Inhumans entirely, still have "inherited powers that can be activated" as a plot point, and keep Kamran as someone who shares an origin with Kamala (in the comics, Kamran was another Inhuman). It lets them expand the MCU just a little bit, and if the series had gone over as poorly as Inhumans did, they wouldn't have closed off another huge power origin.
---Dave
---Dave