Because it has very little binder in it, what is painting over textured wallpaper so often considered though is combining the two . Could just simply be air, just make sure the joints of new paper doesn’t fall on first as it may lift first when drying.
A good oil base primer, as for it’s acoustic and thermal properties, in some areas the plaster has been pulled away leaving defects. It’s an interesting example of the assumptions our minds tend to make against the evidence of our eyes, the paper has been up for well over a month due to changing minds over the emulsion colour so is fully dry. The best results are obtained with an opaque, i would advise though that you throughly prepare your room along with having completed a fair amount of practice or testing prior to spraying your main surfaces.
But to answer your question – this is generally true . If you have silicone caulking around the windows then you need to remove as much as possible, it is in good condtion and I don’t think that the lines in the beadboard will show through the liner paper.