Only a guess, but it could be a simple arithmetic error. Chase Sapphire Reserve offers a 50% bonus (points worth $0.015, rather than $0.01 when redeemed for travel). American Express calls this a 50% Bonus, but it's not, it's a 50% refund which doubles the value of the points.
Going forward American Express is offering a 35% refund, and Chase is offering a 50% bonus. The American Express offer is fractionally larger discount, but for marketing purposes 50% bonus sounds larger.