Sorry, I didn't explain enough. The total commission remains 6%, but if the Seller's Agent split is only 1.25%, the Seller Agent's Broker (most likely) will deny that as the Broker would receive a reduced cut of the commission.
The Seller and the Seller's Agent may be cool with the reduction, but the Broker would ultimately have the final say since it's, legally, their contract.
Yeah, it's usually unequal in the area I used to work in. The Agent's have their own agreements with their Brokers that are independent of any sale/purchase they work on. I've seen everything from 50/50 all the way to 90/10 (10% to Broker).
The Seller and the Seller's Agent may be cool with the reduction, but the Broker would ultimately have the final say since it's, legally, their contract.