I just recently returned from a trip to Portugal, with two flights on TAP - inbound LHR - LIS, and outbound LIS - BCN.

At LHR, an agent was going around at the gate asking random passengers waiting for the flight to get their hand luggage weighed. While waiting in line to board, passengers in line were asked to weigh their hand luggage after their boarding passes were scanned. The two ladies right before me had not only their hand luggage weighed, they were asked to place their personal items on the scale too. All these exceeded the limit (those of us waiting in line were able to see most of what's going on, including the numbers on the digital scale they were using).
To be fair, there were a few passengers who were below the 8kg limit for hand luggage and they were asked to move on to the plane. And I also noticed most that were asked to weigh-in had the rolling luggage.
I had on a backpack and was not asked to weigh it at all. (I made sure it was under 8kg anyway, just in case)

At BCN, not only was there an announcement about this, they followed through with the physical weigh-in as well after boarding passes were scanned. Again, it seemed that agents tend to direct mostly rolling luggage on to be weighed.

From my experience, they were really strict with the 8 kg min. weight limit.