Manx can link in amiga objuect files, has been able to for a long time.
Manx library code was always much smaller than lattice's, this had a lot to
do with the smaller code manx generated. Manx register conventions were
non-standard, but lattice uses them now, resulting in much faster and
smaller code. Manx could always compile large model (>64k data space)
programs.
Lattice has altered the standard amiga object format, not all linkers will
handle lattice created files. I think it is pretty clear that the object
file format on the amiga is not the best, both manx and lattice have made
alterations.