US Citizen traveling from KTM - Beijing, connect through Guangzhou

I am wondering if this is ok? I am traveling to Beijing from Kathmandu for a 3 day stopover. My connecting flight is in Guangzhou. I was under the impression I didn't need to apply for a visa in advance, but the airline tells me I am only able to get a 24 hour direct transit in Beijing because my stopover is in Guangzhou. Has anyone else experienced this?