IJulia build changing conda channel for some python packages within conda environment



When building the IJulia package which is set up to make use of the Conda package and Anaconda most up to date Python 3 installation (with specific sub enviroment ‘conda_jl’ I designated for Julia to be precise), some (8 out of 40 maybe) packages within the sub environment want to be updated through the ‘conda-forge’ channel (no change to the package version numbering whatsoever, only the channel reference).
By the way ‘conda-forge’ channel’s priority for all conda environments is set to the bottom.
IJulia works fine, however when I update the conda_jl environment from time to time with ‘conda update’ the packages get a default update back to prioritized system channel.
IJulia still works fine.
Why would IJulia build process refer to ‘conda-forge’ channel for some packages and reinstall them?