I have that 'problem' too (I don't mind it much) but in reverse. I think the phone because it's a smaller screen and all tries to pick the most important posts only as to not cause it to slow down or be overwhelming on a smaller device.
On my iPad I always use the full FB website rather than the app for that reason as well. But on my Android I get just what FB thinks is the most critical that I read. Most of the time it gets it wrong.