Render Selected should show the reflections of other scene objects - it's there as a way to render just selected objects where those will be composited into the scene in post (e.g. you just changed an object and rather than re-render the entire scene, you want to speed things up by rendering just that object and compositing into the previous render). So Render Selected is working as intended - including reflections, shadows, refractions, GI etc. from the rest of the scene.
For just rendering objects with no influence from the rest of the scene, the native tools to hide objects exist and can be used - but render selected is for a different purpose :)
Alternatively, you could use render selected with Multipass and only use the layers you want (direct, indirect, skip reflections and refractions, etc).