It's NOT Google who notifies you when your Android device has less than 500MB free storage space, but Android OS.:)
The Android >=500MB free storage space rule is because of 'operating capital' - it needs space to store temporary files as you use apps, it needs space to download updates to and space to store the uncompressed update files prior to installing them ( it should delete the compressed and uncompressed update files automatically after install ), etc.pp.
If Android's storage memory is 32GB ( 32,768MB ) then 500MB correspond to ~2%, if it's 16GB ( 16,384MB ) then it corresponds to ~3%. IMO ridiculously low shares. Take note that Windows & Mac computers have the at minimum 10% free space rule.
In answer to your actual question: I don't believe there's a way around this restriction.