TBH this kind of solution is more often pushed by bosses than devs.
Any management person will throw in a "you've done X on this platform, why don't you try to reuse most of your stuff on this other platform ?", just in case it's actually doable.
In my experience as a mobile app freelancer, many prospective clients(=bosses) insist on portable/JavaScript frameworks for new projects. I guess it is because native iOS/Android programmers are expensive, and a single JavaScript programmer rotating between platforms with a shared codebase is both cheaper and easier to manage than two or more native app programmers (at least in theory).
I feel bad for you if you've met such bosses. As one, and as someone who has worked under several, I've never once experienced a boss knowing or saying such things. I've only ever seen it come from developers.
Edit: Just to clarify, there may be instances where a mgmt type has asked if X on platform Y can be reused on platform Z easily. I've never seen it go beyond the ask.
Any management person will throw in a "you've done X on this platform, why don't you try to reuse most of your stuff on this other platform ?", just in case it's actually doable.