Is it standard practice to put the full path to a *.so in a "-l" flag?

For example in groovy:

$ pkg-config --libs rospack
-L/opt/ros/groovy/lib
-lrospack
-ltinyxml
-l/usr/lib/libpython2.7.so
-l/usr/lib/libboost_filesystem-mt.so
-l/usr/lib/libboost_program_options-mt.so
-l/usr/lib/libboost_system-mt.so

Absolute paths can be seen in a good number of standard packages' *.pc 
files.

Why can't we simply put [python2.7, boost_filesystem-mt, 
boost_program_options-mt, boost_system-mt]?

g++ won't take this format, is cmake magically converting these?

- Brian