It's normal for the game to know where your soldiers are once 'revealed'. They might have all been heading for your sniper, until others were seen? The game cheats in this way often. Hence no-one should feel bad using the console occasionally

The aliens weren't activated. I understand that once activated aliens automatically know where the nearest soldiers are. But these were unactivated pods, inexplicably in yellow alert, doing their single moves each turn (visible to my concealed shinobis) all directly towards my soldiers way off in the corner. I've never seen this before, and I've played LW2 a lot.

I don't reload except for things I consider glitches, but decided this qualified (unless someone can explain it to me). I replayed the level using exactly the same tactics as before, and this time the aliens behaved normally. They only went onto yellow alert if they saw a body or I did something noisy nearby, and once on yellow alert they scampered around more quickly, but not in the direction of my soldiers (again, unless I made noise nearby). My concealed shinobis witnessed the usual absurdities of the game that we all enjoy (e.g. two pods move right next to each other, I kill one alien in their midst with a sniper, the survivors of that one's pod activate and start moving towards my distant sniper, the other pod see the dead alien at their feet and go onto yellow alert, but on their next move they run off in a random direction).