Except we're comparing indoors to outdoors. (Although survey quote should be 41% not 48). From that 2nd article:
Figures from the Association of British Climbing Walls (ABC) demonstrate that around 1 million people currently climb independently indoors in the UK, including about 100,000 regulars.* Of these, 59% are estimated to climb exclusively indoors.
Indeed, 71% of independent climbers - those climbing without an instructor - who frequent the wall fewer than once every two weeks, are estimated to climb exclusively indoors, according to the ABC's research.
*Regulars are those defined as climbing once every two weeks (the Sport England definition of regular).