I think the photos are interesting and certainly have a mood about them. I don't understand your concern as to whether Photoshop was used or not. What if they are multiple exposure prints like those by Jerry Ulesmann?
It is certain that they cannot be taken as a single exposure. For the stars to be pin-points, requires an equatorial tracking mount. This would blur the foreground in a circular manner, as the camera is rotated on the mount to match the rotation of the earth against the sky (sky stands still - stars are pin-points). However, when you do this the ground stands still (relative to the camera), and as the camera moves - the ground is blurred in a circular manner.
If the camera was not on an equatorial mount, then the stars would be circular star trails caused by the fixed camera seeing the sky move above the earth. Ground would be clearly exposed, sky/stars would be circularly blurred do to earth rotation relative to the sky.
He could, perhaps, have done multiple film exposures - one for the sky, one for the ground. But, this would take a very intricate setup which would include multiple masks for the different parts of the negative. Much easier to either do the masks in the printing process, or - use Photoshop.
The blurring could be accomplished as part of the printing process without the use of Photoshop. An acquaintance of mine does this all the time by putting a sheet of glass over the paper and smearing Vaseline in different thicknesses just over the area to be blurred. The more Vaseline, the more the blur, the less Vaseline the less the blur.
He also does much of his work through paste-ups, photographing the paste-up, and then manipulating the final print with even more over printing, Vaseline on glass, etc. This also could be the process used to make the prints.
You must think like an "artiste" not necessarily a technician...