Sinopharm didn't revise downwards. Sinopharm just didn't give a day when it would achieve 3 billion doses annual production rate. However, it had enlisted its subsidies and partners in China and also setup two factories with UAE and Seberia to increase production.From what I can see, it looks like Sinopharm vaccine production targets have been revised downwards, but this has been replaced with Cansino.
Astrazeneca is also adenovirus based, and it looks like 2+ billion doses this year.
The Johnson and Johnson single-shot vaccine is targeting 1+ billion
So Cansino at 2+ billion doesn't appear excessive.
CanSino didn't have the capacity to produce 2 to 2.5 billion doses per year. I would think it contracted out production to foreign partners such as Mexico firm Drugmex to increase production. However, firm such as Drugmex is not that reliable as its factory needed upgrade and modernization. And CanSino ended up sending its own stocks to Mexico to alleviate the delays.