Yes, the OneDrive-sync app on the Mac does pretty arbitrary things, as one of the earlier contributors wrote. I have the same problem. Even though I select a directory to be "Always keep on this device", nevertheless OneDrive later on still removes the files locally (or hides them somewhere) with as a result that Apple Quick Look (pressing spacebar to see the content of a file) does not work anymore, and - presumably - spotlight won't be working well either. This makes OneDrive pretty unusable for me as I can't rely on having ALL my files with me when ALL the time when I am offline in a train for example. And no, I cannot predict beforehand which files I might need, I simply want them all. Period.
So, Ankita Kirti, if you finally listen and care to answer to you users: I do want to have ALL my files on my computer, ALL the time, and I do not want any algorithm to decide that I might not need some of them at some random time. This works fine with Apple iCloud, all files I set to be local are and remain local. As I understand that Apple has forced Microsoft to use that same new protocol for file syncing, I do not understand why this could not be made to work with Microsoft as well.
Please note that I had two subscriptions to OneDrive, and I have already cancelled my private one due to this problem. I would really want to cancel the other one too, but can't yet as this is a professional one with no other option yet, but we're looking for alternatives as this simply does not work.