Teardowns I've Worked On
There is a black torque screw to the left of the left side blind hole. It is removed in the photo but no reference to this in the guide. This has to be removed or the board won't slide forward.
The holes simply give anchor point for whatever tool you use to push/pull the logic board from the case. There is nothing released inside of them. Once again if you didn't remove the small black torx to the left of the blind hole, the board won't move.