People do not realize the US has always exerted strong export controls. These accelerometers are most likely ECCN 7A001 (maybe 7A101) and software for their control 7D001 and drawings/specs 7E002 . All highly controlled.
I see no legal reason the border search exemption should be symmetric (incoming/outgoing) since the consequences are different -- inbound contraband can always be later seized; what is lost to outside is gone. DHS should have searched laptop and seized it if controlled material found (as in imminent danger of being experted.) Copy & release was very wrong.
I strongly suspect this ruling will be appealed and overturned, at least in part.