It seems that Hilton recently updated their BRG terms. Now, they have much tougher terms.
Failed attempt example follows:
Please accept our sincere apology for any confusion of the PMG. We've reviewed your reservation and compared it to the rate listed on the screenshot provided. Regrettably, we are unable to honor your claim as it did not meet the criteria to qualify for the Hilton Price Match Guarantee. The screenshot includes an Easter discount, not eligible for this program. The screenshot is incomplete, immediate confirmation is not confirmed, the rate requires prepayment and is not comparable to the rate booked and confirmed through Hilton. The confirmed booking is immediate and does not require pre-payment.
Official terms follow:
Difference in terms You booked a fully refundable room but this price is for a room with a 100% credit card deposit required upfront
So maybe all prepay but refundable are not accepted anymore? As in Hilton refundable rate will be paid at hotel.