Make sure you specify the correct things, e.g. printed area is not the same as paper size (if that's what causes the issue).
Turned out that this was an issue of Qimage not updating its crop/border limits when virtual paper size changes (borderless vs. non-borderless) or the print driver is changed. It can be forced to update them which then allows me to set the correct crop size.
Here is a screenshot that demonstrates how Qimage does properly read out the (virtual) paper size from the driver, but it may still inflict the lesser printed area boundaries of the smaller physical size when its crop parameters are not forced to update.
The last part shows one problem with Qimage. In order to get 1:1 crops/prints I would have to zoom the crop to exactly 360 dpi, but the zoom lever is not precise enough and thus jumps between 359 and 362 dpi in a single step. There is no way to enter the zoom factor / DPI manually.
There are some more issues, one of which is that Qimage tends to run out of memory with these large images and then more and more errors creep in or options cease to function unless Qimage is reloaded.
I also noticed that various TIFF files cannot be loaded with my test image.
Qimage cannot load the following TIFF files:
ACDSee uncompressed, LZW, ZIP
FastStone ZIP
Gigapixel uncompressed, LZW, ZIP
Photoshop uncompressed
QImage can load the following TIFF files:
FastStone uncompressed, LZW
Gimp uncompressed, LZW, ZIP
IrfanView uncompressed, LZW, ZIP
Photoshop LZW, ZIP
XNViewMP uncompressed, LZW, ZIP
Furthermore it cannot load Photoshop PNG.