Okay in verbose this is how program ends -
Code:
Info(prcgen):I15000: Approximate Standard Mobi Deliverable file size : 4184073KB
Info(prcgen):I15001: Approximate KF8 Deliverable file size : 0003591KB
Info(prcgen):I1036: Mobi file built successfully
I'm assuming that it just is simply not trying to combine them into a single file, either because there is a binary it wants not present or because there is a bug in the Linux version.
It's not uncommon for commercial companies with closed source software to not really care about their linux builds.