As requested, I did a comparison with Polaris, given its high DEC value. I also examined the difference between Telescopius and Kstars when calculating the image centers for a selection of coordinates where the RA is 0 and the DEC is 0, 30, 60 and ~89 degrees.

Whilst both tools act a little differently at high DEC approaching 90, there was a clear indication that the calculated Telescopius RA position relies on a factor applied by cos(DEC).
For most coordinates where DEC is say <85deg, the Kstars value can be corrected by dividing by cos(DEC).

This table shows the comparison. I used an online tool to covert the RA and DEC to degrees so some rounding issues may exist, though the relationship is clear - until it breaks at high DEC.

dmsummers was right on the money with cos(DEC), I don't know coding well enough to fix it and I don't know how to stop the crazy values at high DEC.

Hopefully this work fast-tracks a solution. Plotting a mosaic grid in Telescopius then manually creating jobs in Kstars is going to be painful... (but not impossible).