If I’m reading the specific function that does the outdated udev rules check right, (so you’re getting the ‘outdated’ rules message, not the ‘please install’ message?), it seems like the comparison is being done against the copy of the udev rules included at .platformio/penv/lib/python2.7/site-packages/scripts/ in your home directory… i.e. Linux: ~/.platformio/penv/lib/python2.7/site-packages/scripts/ or Windows: %USERPROFILE%/.platformio/penv/lib/python2.7/site-packages/scripts/
You can also compare it to this version, which is the one for 3.6.7 (it’s from the master branch, not the develop branch), and can be installed like :
curl -fsSL https://raw.githubusercontent.com/platformio/platformio-core/master/scripts/99-platformio-udev.rules | sudo tee /etc/udev/rules.d/99-platformio-udev.rules