Binners, the aim is not to staff the Army with reservists, but to retain a core of, what, 80k full-time professional soldiers and bolster them on ops with an increased number of Reserves. The aim, as far as I can tell, is also for the Reserves to get increased training and to morph into an organisation that can more easily slot into a regular formation when their skills/manpower* is required.
The TA is changing and the name change is, I think, an attempt to reflect that change. The days of going to the TAC for a couple of hours of tarting around with Ptarmigan before heading out for beer are long gone. This is the start of what is hoped to be a better skilled, more highly trained and close-knit Reserve formation.
*dependent on trade.