It's all in the title.
This:
simple.d
---
void main(){}
---
compiled as
dmd -m64 -ofs64
gives following:
s64
s64.obj
where s64 is indeed the application but without .exe suffix.
dmd -m32 -ofs32
gives the usual:
s32.exe
s32.obj
Seems like a trivial thing but horribly annoying.