In 1940, a group of American fighter pilots volunteered to go to China to fight on the side of the Nationalist Chinese forces against the Japanese. They were called the "American Volunteer Group (AVG)". The official story was that these were people who had resigned their commissions in the US military and went over (because, of course, if they were officially still US military officers, and were shooting down Japanese planes, then it would of course be an act of war, and give the Japs an excuse to retaliate by, for example, attacking US military forces in Pearl Harbor)
My point is that reports probably were coming back of Chinese personnel working with the Taliban, and the logical assumption being that the Chinese government wouldn't be allowing them to cross the border into Afghanistan unless the Chinese govt wanted them there. It's very unlikely that Chinese support for the Taliban would consist of people in official Chinese uniform.
Debka claimed that the Chinese government sent 3,000 troops overland by truck to Afghanistan. Problem is, the Northern Alliance controlled the overland route, the narrow corridor that connects Afghanistan to China. And there definitely weren't 3,000 Chinese troops there - Rumsfeld mentioned a handful of volunteers, not thousands. So the Debka story was wrong. As the saying goes, the devil is in the details.