pipreqs does not show versions of the packages correctly in the conda virtualenv

I have Flask and matplotlib libraries installed in base and their versions are 1.0.2 and 3.1.1, respectively. On the other hand, on conda virtualenv has the following versions. enter image description here When I listed packages using pipreqs to create requirements.txt file while I am working in virtualenv, I see that the versions of libraries do not match with the ones in virtualenv. enter image description here Versions listed with pipreqs consistent with the those in base environment. Does anyone know why I am having this problem? Any help would be much appreciated.