It seems like shove uses a different way to calculate LoS/perception compared to regular attacks. I don't think this behavior is intentional, since shove typically also counts as an attack, and I'd therefore expect it to work similarly.
In the tooltip in the first screenshot (I hope) you can see that the my fighter does not have line of sight with the orc when trying to attack normally, due to the fighter being behind full cover. (If the mouse was included you'd also see the red cross over the cursor.)
The second screenshot shows the tooltip when "shove" is selected. Here I can target the orc just fine and shove him down the ladder, which I did (muahaha). The mouse cursor that you cannot see showed a gear, similar to when interacting with a block or door or trap. So maybe shove uses "interaction" rules instead of attack rules when determining LoS?
Hope we get to beta-test this, too! It's almost more fun trying to break the game (and succeeding!), than getting a smooth polished game experience.
Keep up the good work,