Nowadays its quite common to see the project changing their rules whenever the campaign is near to an end. Sometimes they are extending it or suddenly requiring the participants to comply in kyc.
Its really disappointing but we have no choice but to abide to their new rules to get the rewards that we deserve.
Many bounty rules always state that the have the right to make changes.
Well you're right, its possible for them to change the rules thus if you understand what this means you wont be surprise if changes has been made.