These conditions have changed significantly in the next build to be a lot simpler, as part of re-working them to support OR blocks. I'd recommend you wait for r88 to be released (out shortly) and check the source again then. 'Is overlapping' is no longer a static condition in r88.
FWIW, static conditions don't do any picking - basically the runtime will run the function once instead of calling it for each instance, and it's the function's job to do all the necessary picking. It just needs to return true/false, and as per usual javascript if you return an array length or some other number it is true if it is nonzero otherwise false. However, it can be very tricky to get static conditions right, so I wouldn't recommend them. 'On collision' for example uses retriggering to run the event manually which is why it returns false.