The Ryzen 5 1600 and 1600x have two CCX modules with 3 cores each (one core disabled on each CCX). So it wouldn't be impossible for AMD to make a 14 core part.
If this applies to multi die solutions like Threadripper, there will be no 10 and 14 core parts as they would require uneven CCX combinations.
If the Epyc lineup is an indication this might be true. Especially since there is no 12 core part for Epyc. Since it has 4 dies you could produce 12 cores by using only 3 cores of each die, but this would require uneven CCX (1+2 or 0+3).
IOW core #13 is the 5th core in the second die, aka the 1st core in the second CCX on the second die. So it would have a direct link to the 1st core in the first CCX on the second die, as well as a link to the 5th core in the other 3 dies as well as a link to the 13th core on the second chip if in 2P.
So it seems quite likely that all 16 CCX's in a 2P server must have the same number of cores.