Yes it's 75kg
It's confirmed in the OEM bar installation instructions, look for PZQ3089050 here:
https://toyotamanuals.com.au/accessoriesIt's not overly clear in this one, but does state "- Total load to be carried on Toyota Roof Rack System is 75kg maximum for on-road and off-road driving.".
I have another version pdf from Toyota for gen 8 that is a little more specific in pictograms and noticeably different in that it gives maximum total weight (including the 6kg bars) as:
On-road, 120km/hr 75kg
Off road, <120kh/hr 45kg
Can't recall where I got this one from.
The awareness level is a bit surprising though as the concept has been clearly documented with Hilux and also other bars I've previously fitted to my various other vehicles from other manufacturers over time.