As mentioned in the article, conditions of carriage have stated this limit for over ten years.
At best a helpful deterrent and might help put a few people off carrying multiple suitcases, but actual enforcement will be very rare IMHO▸ . After all this is a limit per passenger and ‘one large suitcase, a carry-on bag and a small hand bag’ should be all an individual should ever be able to sensibly manage anyway.
It is a good idea I think and as you say the "limit" is a reasonable one - you do wonder how anyone could physically carry much more than that anyway! (Although having accompanied my wife on her shopping trips to act as a mule, I've had a fair bit of practice!)