The Auscycling Statistics (2021) claim that mountain biking is 1.6% of the population (this includes children aged 0-9 years old). Their 2022 Statistics update upgrades that to 2.2%.
Roy Morgan statistics (2021) claim mountain biking is 1.4% of the population:

Roy Morgan Top 20 Sports 2020/2021
No. 1
Walking 51.9%
No. 6
Cycling 6.4%
No. 7
Bushwalking (during Covid) 5.2%
No 9
Golf 2.6%
No 18
Mountain Biking 1.4%
And these four other recreations will be damaged by building the mountain bike destination:
Bushwalkers are already being run off their trails by mountain bikers who do not care about signage or advice about walking only trails – they will not listen to you if you tell them not to. An increase in Mtb tourism will make it worse. They ignore DELWP but the problem with the mountain bikers only started in 2014 AFTER the release of the Mountain Bike Feasibility Study.
Walkers on the RailTrail and around the river walk are already suffering due to excess traffic and are avoiding the trails either altogether or at peak tourist times. Dog walkers, the elderly, women with children and horseriders are the most vocal about the lack of amenity on the RailTrail right now. Do you care?
Cyclists – there is a prediction that traffic of bikes on the Warburton Millgrove section of the trails will more than triple. This extra traffic will be mountain bikes that have trails that ascend from descend to the trails. We are concerned that families with their kids or the elderly out for a gentle ride are not going to enjoy what is already an overstretched facility if it is dominated by male mountain bikers between the ages of 30 and 50.
Horse and Pony Clubs – horses spook when mountain bikes flash past or loud or unusual noises are made nearby. How is that to be managed? You can’t. And there are little kids on those horses. Where is the duty of care?
Off Leash Dog Park – dogs spook too, sometimes that means they chase and attack bikes and sometimes that means they will run away and hide and yet the project is taking a third of their space for parking and they will have mtbers all around them
Golf – Golfers will be negatively impacted because the Golf Club will be the Mountain Bike Hub in Warburton with a mountain bike trail running the full length of the Golf Course and the Club rooms and parking will be given to mountain bikers for their use.