It's a test facility. They have to take the aircraft out from overhead cover in order to actually test them. Testing only at night would be much too restrictive.
They track all observation satellites and meticulously schedule aircraft movements for when they're not observed. The problem is Planet Labs alone has over 200 satellites, and that's in addition to other commercial imaging providers and all the governmental earth observation satellites. That means in recent years the margin for error has become increasingly smaller.
Given all that, while it's certainly possible this was deliberate, I don't think it at all implausible for it to be accidental. Some occurrence that delayed them by just a few minutes could potentially have caused this.
