OK here comes the experiment.
file1.asm:

$mod52
   mov  a,#2
$include(file2.asm)
   mov  r2,#3
   end

file2.asm:

   mov r0,#2
   add a,r0

Assembled as per OP using metalink's assembler.
The resulting file1.lst file

FILE1                                                                                                         PAGE 1

                       1    $mod52
0000 7402              2       mov  a,#2
                =1     3    $include(file2.asm)
0002 7802       =1     4       mov r0,#2
0004 28         =1     5       add a,r0
0005 7A03              6       mov  r2,#3
                       7       end

VERSION 1.2k ASSEMBLY COMPLETE, 0 ERRORS FOUND
FILE1                                                                                                         PAGE 2

Now, tell me, is it really HARD to figure out what has been included and from where????

This is THEIR OWN assembler, I suppose they have read THEIR OWN documentation!

If a tool does not do what is expected to do (an emulator is expected to show the instructions executed), it IS FLAWED.

Jan Waclawek