This has something to do with how MacOS deals with monitor settings. If you set your monitor to 1800 x 1169 pixels, and MacOS would simply use that, then everything sent to the screen would be upscaled to 3024 x 1964 pixels, because the hardware resolution obviously remains what it is. That would make it look soft and fuzzy, so MacOS uses a trick. It tells all apps that the screen is set to 2x (1800 x 1169) = 3600 x 2338 pixels. Now it can downsize that to the native 3024 x 1964 pixels, and so it remains sharp and crisp.
Unfortunately, not all apps deal with this correctly. This upsize/downsize trick should ideally only be used for interface items, not for images. If it is used for images as well, then displaying the image at 100% means the app will sent it to this virtual 3600 x 2338 pixels screen at 1 image pixel = 1 screen pixel. But then this gets downsized 3024/3600 = 0.84x. So your image is not really shown at 100% but at 84%. Unfortunately Lightroom is one of the apps that does this. Apparently Apple Preview works correctly.
BTW, I have discussed this issue with Adobe countless times, but either they don't think this is important enough to fix it, or they don't have a clue how to do that. I have given up on this. If you would set your monitor to exactly 50% of the native resolution (so to 1512 x 982 pixels in your case) then everything will look correct, because in that case 2x your screen setting is exactly the native screen resolution, so there is no downsampling.
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