RPATH in embedded binary: image not found while path is Okay

Question

Since DYLD_LIBRARY_PATH is ignored when SIP is active I am trying to use @rpath instead. I understood that one can add several @rpath and that the system will try all of them successively to find the library. I also understood that RPATHs propagate from loader to libraries and dependencies. Am I right ?

Unfortunately all my attempts to use RPATH failed so far. The auxiliary binary (embedded binary) "grasp" tries to access libraries located in a folder external to the bundle (see a description of the bundle at the end).

Here the environment variable which works if SIP is not used:

DYLD_LIBRARY_PATH="." DYLD_LIBRARY_PATH="$DYLD_LIBRARY_PATH:/Applications/MATLAB/MATLAB_Runtime/v911/runtime/maci64" DYLD_LIBRARY_PATH="$DYLD_LIBRARY_PATH:/Applications/MATLAB/MATLAB_Runtime/v911/bin/maci64" DYLD_LIBRARY_PATH="$DYLD_LIBRARY_PATH:/Applications/MATLAB/MATLAB_Runtime/v911/sys/os/maci64"

Here at the bottom, the RPATH I added to the binary "grasp" using command:

install_name_tool -add_rpath <absolute path> grasp

otool -L grasp.app/Contents/MacOS/grasp
    @rpath/libmwlaunchermain.dylib (compatibility version 0.0.0, current version 0.0.0)

otool -l grasp.app/Contents/MacOS/grasp | grep -B 1 -A 2 LC_RPATH
Load command 19
          cmd LC_RPATH
      cmdsize 32
         path @loader_path (offset 12)      <-- present in the original binary
--
--
Load command 20
          cmd LC_RPATH
      cmdsize 32
         path @loader_path/. (offset 12)      <-- present in the original binary
--
--
Load command 24
          cmd LC_RPATH
      cmdsize 64
         path /Applications/MATLAB/MATLAB_Runtime/v911/bin/maci64 (offset 12)

Nonetheless I still get the error message:

dyld: Library not loaded: @rpath/libmwlaunchermain.dylib
  Referenced from: grasp.app/Contents/MacOS/grasp
  Reason: image not found

I thought that

@rpath/libmwlaunchermain.dylib

would resolve to the path to the library

/Applications/MATLAB/MATLAB_Runtime/v911/bin/maci64/libmwlaunchermain.dylib

Why does this fails? Is this due to "grasp" being an auxiliary binary? How can I debug that?

Bundle organisation:

Grasp4Mac.app
    Contents
        MacOS/mylauncher  <-- launches grasp.app
    Resources
        Grasp/graps.app    <-- embedded bundle
            Contents
                MacOS
                    applauncher <-- main
                    prelaunch
                    grasp  <-- auxiliary binary calling the libraries