Yea, ideally the common code base (such as network interface and browser integration) should be shared across platforms.
this is what Dahua is doing now. You have some shared elements - like base, HTMLPlayer, web ui which are regularly rebased.
But strange changes (like speed limits done for footage
downloads) done individually in each firmware line stays.
Those elements and theirs versions are displayed in camera system info page.
They should move to Unifi Protect (or iPhone) model. Where you have simply one MAIN software line.
And each camera / iPhone models receive the same updates (with HW / model limits applied).
Latest Unifi Protect version is 6.1 (example).
And the same version is released for all Unifi NVR's and supported Unifi cameras.
all new features are implemented everywhere (of course if HW allows, for example older cams with weaker SOC don't have never AI features).
then system looks very unified - even if you have big mixture of different camera models