“When you do your business, you just don’t look down,” she said. “I’m not satisfied with such a toilet, but you don’t really have a choice. Our economic conditions are such.”

But China’s toilet revolution has led to excesses — a problem that critics say could plague the Gates effort as well.

To win favor with Beijing, local officials have tried to outgun one another with newfangled latrines, many equipped with flat-screen televisions, Wi-Fi and facial-recognition toilet paper dispensers. (Thieves have been known to make off with entire rolls.) There were even refrigerators, microwave ovens and couches, prompting China’s tourism chief at the time to instruct officials in January to rein in their “five-star toilets” and avoid kitsch and luxury.

Though the products on display on Tuesday were nowhere as flashy, Mr. Gates has drawn criticism for giving thousands of dollars to universities in developed countries to create high-tech toilets that will take years to pay off — if they ever do.

“Sometimes doubling down is necessary, but you’ve got to be reflective,” said Jason Kass, the founder of Toilets for People, a Vermont-based social business that provides off-grid toilets. “Has any of the approaches done in the last five years created any sustainable lasting, positive impact vis-à-vis sanitation? And the answer, as far as I can see, is no.”