Gamma chart looks different in Preview vs Safari

I need to back up some as my test missed something critical. All methods of viewing that chart look pretty close when I set my display to view at the native 4K resolution. If I view them at my general use display settings (Settings->Displays) of 3008x1692 then I see the browser issue with the chart. When I viewed them in my apps I followed what the instructions said and set to native 4K but I did not do that with the browsers.

One thing that I saw in the page that the chart comes from is that the chart must be viewed at the native resolution of the display and assuming that also means that the image must be scaled precisely to 1:1 for that resolution, i.e. the 990x768 pixels of the chart must be viewed at exactly that many pixels on the the display. Are you sure Resolve is display at that exact pixel to pixel match? Also, the browser issue is still there when I view those charts when my display is set at its native 4K resolution.

So, If viewing at any other display resolution settings, all bets are off as far as the usefulness of the chart.

I have verified the behavior you are seeing and I have an LG27UP600 which is a 4K display set for DCI-P3 with basic calibration (using the advanced mode in Apple's color calibrator to create a profile). Just to note, I have the HDR mode disabled in the Mac Display Settings.

I have also opened it in two of my photo apps and it shows the 2.2 gamma that I had calibrated for.

In addition, I opened the website in Microsoft Edge and saw the same results as Safari. So the issue is not just with Safari but how the images are being rendered in the browsers. I don't have a PC so I don't know if it is a browser rendering issue on Macs or a general browser issue.

What Monitor?

I asked on the monitor because some are very smart & change things on their own if it thinks it's Video, TV, Sports, Games, etc... it was the only fishing trip I could think of.