The simple fact is that if OP was booked in Business and could not be accommodated in that cabin, he is due a refund of 75% of the base segment fare. The offer of flying 24 hours later is a red herring insofar as his question is concerned.

To be clear, there is nothing wrong with having made the offer to OP. Many people would be quite pleased with an extra day. But, that is absolutely the passenger's choice.