Oh thats block 123297, ok.
Yeah, its not DGW in this case (You will see more like a 1k-2k reduction when diff is > 90,000) but this diff is just 25K, not a big deal (probably a 500BBP reduction) but anyway the large change occurred at block 123201 (Evo cutover height).

At this height bbp started escrowing additional for GSC contracts (which are 1mm bbp per day, deflating as usual).  So the normal reward was about 10K for heat, with it being 5.4K the remaining 4.6k went to the GSC budget.