I can definitely confirm that the aliens will still attack whoever has the lowest PSI Strength (no soldiers have PSI skill yet in my game).
That actually brings up a question I have. How do aliens gain targets for PSI attacks? I remember in the original TFTD and UFO they had some weird rule that if the aliens could see any of your soldiers then all of your soldiers can be targeted, and they remembered your soldiers' positions for a few turns after (so they could keep getting targeted). This resulted in a bunch of guys in the back of the Skyranger/Triton getting attacked all the time. It was one of the lamest and most frustrating things about the original games, resulting in me quitting the game on multiple occasions. Even though I know how to deal with that now, at the time as a kid, it felt so impossible to overcome.
In my most recent encounter in X-Com Files, I had some guys outside of a UFO with the leader inside. Once some of them approached the side of the UFO, they started getting attacked. There was no way any of my those soldiers were able to be seen by any alien (though some other soldiers did get spotted a few turns past. Do the leaders have PSI sense, or is the targeting just like old-school UFO/TFTD?