Maximum contrast ratio for good accessibility

So we are remaking an enterprise app from scratch. This time we want to do base our design decisions on proper research.

Our users use the app 24/7 with high requirements for UX. So our main goal is to make everything as easy to use and accessible as possible.

We used to have 2 color themes in the app: "day theme" (default, with light colors) and "night theme" (aka "the dark theme", for those who work at night). This time around we're having 3 themes: "day", "night" and a "high-contrast" one (aka the "accessibility theme") and we try to be WCAG2.1 compliant where we can.

Now, everything's good with the "day theme" (WCAG Level AA) and the "high-contrast theme" (WCAG level AAA), while we have some problems with the "night" one - users argue that WCAG Level AA is "way too contrast" ("too bright", "bad for my eyes") for working at night.

We've checked some other standards and guidelines, but they all talk about minimal requirements and never discuss the maximum.

Guidelines for newly released macOS "dark mode" state

For custom foreground and background colors, strive for a contrast ratio of 7:1. This ratio ensures that your foreground content stands out from the background, including when Desktop Tinting is active. It also ensures that your content meets more stringent accessibility guidelines. At a minimum, make sure the contrast ratio between colors is no lower than 4.5:1.

Which goes well with what we try to do with our night theme. We pass the Material Design guideline recommendations and Windows design guidelines too.

While, for example, Adobe Photoshop's darkest color theme has the ratio between small text and buttons drop to below 4:1 at times.

So my question is: is there any known research or standards that set "maximum caps" on contrast for working at night? Maybe some health implications for contrast being too high? Some other reasons not to maximise the contrast?