As you might or might not know, northstar does not save playtime to steam and i have not seen anyone address this.

So first open the local files for titanfall 2 (right click then browse local files) and find the path for northstarlauncher.exe and right click the file and copy as path,

Now right click titanfall 2 and open properties then add the path that you copied and add %command% at the end.
(example: "E:\Steam\steamapps\common\Titanfall2\NorthstarLauncher.exe" %command%)

Once done it should launch northstar and save your playtime from whenever you play it now.
(If you want to remove it to get the achievements or any other reason, just remove the stuff from properties.

Full credit to: https://youtu.be/b2oRsskWBRM for letting me discover this method.