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Your CTOT may have come forward because your company has listed your flights as RFI - Ready For Improvement. This means that the flow computer will automatically issue an improved CTOT regardless of whether or not you have had an REA - Ready message, sent.
It is therefore your responsibility to either get all your pax on board in time (difficult when there is so much shopping to be done!) or ask your company not to list you as RFI and wait until you are ready to send the REA.
As others have said, flow measures do sometimes come and go very quickly which can cause problems in knowing whether or not to board pax. Surely it is better to get them rounded up an hour early rather than depart an hour later than you could because you couldn't find them in time? This would also permit airports to remote park you so that the gate is freed up, the tug can be released and you're in pole position should an improvement materialise.