Actual enforcement varies IME.
I've been checking in and my cabin bags haven't been weighed while at the adjacent checkin the passenger has been forced to repack to keep to the exact limit.
Other times they have been weighing everything but not to bothered about people who are a bit over.
And I've never had stuff reweighed when boarding a connection at DXB - but I've heard complaints that sometimes they do and it can be expensive if you are well over. Saying it was allowed on your first sector isn't a viable excuse.
I would add that 7Kg is pretty lousy - some camera gear and a small laptop and odds and ends can easily go above that. Allowing some flexibility just encourages chancers and is unfair on those who make sure they comply. I think a 10Kg limit with absolute enforcement - checkin weighing and regular gate checks - would make life a lot easier and actually be fairer.