Okay so recently I tried a tactic where I send my squads out from an outpost at end of tick and immediately lock it down that tick after sending, to trap attacking squads. After refreshing twice after doing both it showed up as my squads having just left and the lockdown in place.

Now it is important to iterate that I did these same tick, just the lockdown after I launched. Next tick, I got a battle report saying that the attacking squads landed and kill my squads who had been fleeing.

Now, I know the wiki says that squads leaving an outpost/colony that gets spied would still be damaged, does this go for lockdowns too and thats why my squads got stuck on the op? Or is it a glitch I need to report?

My first guess would be you launched with a delay. If your units were supposed to leave BEFORE the enemy landed, your units should of been fine. As long as they said they were still moving away BEFORE the lockdown occurred. If it was after though, you wouldn't of been able to see your units leave anyways due to the lockdown.

But delayed movements will act as if you hadn't moved yet (though if you are locked down while you had units on delay, they will keep to that delay regardless of the lockdown as long as you don't recall).

So if everything you said was indeed correct, this would of been a bug and should be reported. Unfortunately, nothing we can do about the lost units, but we can at least look into it to try to ensure it doesn't happen again (or if it was indeed due to a user mistake). You live and you learn though if it was simply a mistake.