As you can see from the below screenshot 800x600 resolution is not as it should be:

Well, it's as it should be... sort of. On macOS and iOS, there are "physical resolution" and "logical resolution". For instance, iPhone 15 Pro Max has physical screen resolution of 1290x2796, while it's logical screen resolution is just 430x932. So when you are setting the window size, you are setting it in terms of "logical pixels", not "physical pixels", while the list of available resolutions is probably taken from the "physical" display parameters.

macOS by default does not set the highest resolution (which makes sense for 13" display):

Not only for macOS but for other OSes we shouldn't allow to even select resolutions which are higher than the one is set for display. However, this could be a big change in terms of testing. We can limit the change to macOS at the moment.

What do you think @oleg-derevenetz ?

Not only for macOS but for other OSes we shouldn't allow to even select resolutions which are higher than the one is set for display.

If there is a portable way how to do this (using SDL), then we can introduce a restriction of this kind.