AFAIK anything past 32,000 is digitally expanded (which could be done with RAW post-processing).
EDIT:
See: https://www.photonstophotos.net/Charts/RN_ADU.htm#Nikon%20D5_14,Sony%20ILCE-1M2_14
The old Nikon D5, impressively, doesn't seem to post-scale even at ISO 102400