yes.. I did this experience. it is nowadays becoming habit of every ICO project. first they make big promises to give high rewards for bounties. but when bounty and ICO finish they find excuses to reduce bounties.
sometime they say they didn't get proper results. sometime they say they have other bounties in other platforms..
but sometime it happen because of ICO result also which is not the owners fault.. if ico raise less funds then bounty tokens will also reduce. that is logical.