Is any of this confirmed or is it conjecture?It would be manned by Afghan government forces but will also have a Chinese presence. Construction will mean Chinese contractors/army engineers, bringing in Chinese troops for security. Training of Afghan forces will be provided by China, necessitating Chinese troops.
China has built other infrastructure projects in Afghanistan without needing to deploy PLA troops as security.
Any troops Afghanistan provides would already be trained, and any additional training needed on new weapons and equipment should be minimal at best, as I seriously doubt China will be supplying much more than what the Afghan forces are already equipped with.
Any Chinese presence in the building of the base will be limited in both scope and duration.
Afghanistan is a worthless backwater without anything of worth to fund its development, which makes its people vulnerable to exploitation from warlords and foreign extremists.
Even a small sum to most people is probably a small fortune to locals. And with little to no education and medieval moral norms, if you flashed some cash, you will probably literally have a line of locals willing to dust off their ancient AKs and shoot whoever you ask them to.
When those poorly armed locals with next to no training try to attack professional foreign soldiers, the inevitable happens and they come home in body bags riddled with bullets, and the foreign soldiers now have a blood feud with half the village.
China would be stupid to want a piece of that crapcake.
China want an Afghanistani staffed military base on its boarder to police that area to stop extremists coming across before Chinese boarder security have to deal with them on Chinese soil. It is willing to pay for its building and upkeep, but what it does not want is Chinese boots manning it.
The whole point of the base is to stop extremists, so that means patrols and combat.
No matter how well trained or equipped, soldiers will die on such combat patrols, and any insurgents those soldiers kill in turn will have friends and family who will want blood for their deaths.
The literal whole point of this base is to stop, or at least massive reduce, Chinese security forces casualties and prevent China from becoming a target for extremists by not have extremists die by Chinese hands if possible.