Global Express/XRS Flight control synoptic page
After engine start, the flight controls are cycled through their range of movement and this is monitored on the synoptic page. The flight controls themselves can't be seen from the cockpit. I would suggest that it's human nature to assume all is well and you are looking at the range of movement indicated, not actually comparing the direction of movement of the multi-function spoilers to the ailerons. I can't recall if the FCOM (or equivalent) called for the checking of the roll function of the spoilers specifically or simply a check of whether they extended manually and "automatically" (weight on wheels). If you look at the diagram above, it has a top section and a bottom section. One tends to look at the bottom section when checking the primary controls and then the top section when you move on to the spoiler check. You therefore may not notice the asymmetry. I have seen pilots who come off the G-IV do the spoiler roll check out of habit, as the G-IV had a reasonably detailed ground spoiler check in the after start checklist.
This would have been an extremely confusing event for the pilots. With initial roll input, all would have worked correctly. Increasing the roll input, thereby activating the roll spoilers, would have reversed the desired result, which would trigger your muscle memory to further increase the roll input, again accelerating the error. Near the ground, it would take a quick thinking and brave individual to try reversing the roll input, potentially making the situation worse.
The crew did have a chance to trap the maintenance error in the after start checklist but this is yet another classic Human Factors incident with plenty of learning lessons. I'm glad the crew are ok. They did a good job recovering the aircraft.