Several companies, including Consumer Intelligence Research Partners and Mirabaud Securities, said recently — in different terms — that demand for Apple's iPhone X had been weakening in the March quarter.

Several analysts and banks have suggested in recent weeks that demand for Apple's most high-end iPhone, the iPhone X, has been waning.

But Apple has an enormous supply chain, and the reports from a few of Apple's suppliers may have led analysts to get the wrong impression about iPhone sales for the March quarter, particularly sales of the iPhone X.

In fact, in Apple's earnings report for the quarter ended March 31, the company said Tuesday that the iPhone X is still outselling its other iPhones. It's unlikely that's dramatically changed in the first couple of weeks of Apple's fiscal quarter that started April 1 as some analysts have suggested. (Still, many analysts fear Apple's sales will fall off during the current quarter.)

"The iPhone X was the most popular iPhone each and every week of the quarter," continuing a trend that began when it hit store shelves in November, CEO Tim Cook told CNBC's Jim Cramer on "Mad Money."

"The iPhone X has been a huge success and it's the first time since we split the lineup back at iPhone 6 and iPhone 6 Plus that the top model has been the top-selling model," Cook said.

Apple still missed estimates on iPhone unit sales. It sold 52.2 million iPhones during the quarter versus 52.54 million units expected by a StreetAccount estimate and fewer than Goldman Sachs expected. The average selling price of an iPhone during the quarter was $728 while Wall Street expected an average selling price of $742.

China also helped drive the iPhone X's success. Cook said the model was "the most popular smartphone in all of China last quarter." (Jun Zhang of Rosenblatt Securities said in April that sales of Apple's new iPhones were cooling down in Asia.)

"As I predicted, Apple's iPhone X was its best-selling phone in a time that other financial analysts were saying the phone was going to be killed," Patrick Moorhead, president and founder of Moor Insights & Strategy, told CNBC. "Every product line improved, led by services (31 percent) and other (38 percent) but Macs were flat. This says a few things. IPhone X has staying power and stickiness, Watch and AirPods are very successful, and services are huge, a $12 billion run-rate business. The iPhone staying power gives the company time to get its HomePod business humming while the industry awaits AR and VR to kick in the next three to five years to provide growth."

Moorhead said in April that suppliers may see a decrease in orders as Apple seeks other providers for parts. KGI Securities Ming-Chi Kuo has suggested Apple may launch three new iPhones in September, including an upgraded model of the iPhone X.

Some banks believe that decreased iPhone sales — not just the iPhone X — will be reflected in Apple's next earnings report, however. Bank of America Merrill Lynch and J.P. Morgan specifically blamed Taiwan Semiconductor's weak guidance for the March quarter. Goldman Sachs also slashed iPhone estimates for the June quarter.

— CNBC's Anita Balakrishnan and Sara Salinas contributed to this report.