Why wouldn’t more of them simply form like a star with star having the same orbital mechanics, while rogue planets ejectide from a planetary system would tend to be captured elsewhere or escape out of the galactic plane and into intergalactic space?My guess would be that I am right, and you are right, and 'it' happens in some ways we can't even imagine.
It is 'possible' in an 'infinite' universe for 'everything' to happen.
Most solar systems are likely a mixture of 'created' and 'captured' planets.
For instance, it has been accepted that most planets in our Solar System are 'created'. However, Uranus may have been captured. It has a vertical rotation, rather than horizontal like the rest.
My main point was that matter surrounding a star would become stratified like the rings around planets, and if that is true, then it would help explain the makeup of the different planets in a solar system.
Many of the hypotheses and assumptions in the past fifty years concerning the development of planetary systems have been demolished in many respects by the recent exoplanet discoveries. Whereas it was formerly thought that the stellar winds would remove the lighter gaseous elements from the inner planets to be swept up by the outer planets to produce Jovian class gas giants, we are now finding many gas giant and super-giant planets in orbits comparable to our Mercury and even closer. Once again, experiment and discovery are demonstrating how the real world is so often stranger than human imagination.