Are there many Muslims who serve in PLAN to make this question more relevant than it is?
Well, using Muslim to denote those service men and women in PLA will lead to the same confusion in the "fight". In China, government employees (PLA is part of) can not be religious. So a Muslim in the western definition is not let into the institutions, same for Christians or any others. However, an ethnic minority such as Uyghur can join PLA and eating exclusive food on the ground of ethnic customs and traditions but not religious ground. He/she can be admitted into CCP which is a prerequisite of being promoted to officer. Now you can ask is he or she a Muslim or not.
On board Liaoning, there are 25 always using this Canteen. I presume there are at least 25 Ethnic minority sailors/officers who are from such background that they exclude certain food. But I am sure they are not religious. So they are ethnic Uyghurs, Kazaks or Hui's, but not Muslim in the non-Chinese sense. There are many posts in this thread some time ago about Uyghur sailors on Liaoning.
In other branches in PLA, I know there are some company sized units in Xinjiang being primarily composed by soldiers from certain ethnic groups. These units have their own facilities to server their special need including food. So, it is very relevant to certain units and areas. I think
the relevance does not need to be related to the number of soldiers, it is an official principle enshrined in the state and party constitution in China.
A background infor., the current Chairman of Xinjiang Shohrat Zakir is Uyghur and CCP member, the former deputy prime minister Hui Liangyu is a Hui and CCP member. Both Uyghur and Hui are traditionally Muslim people, but now many of them are CCP members and state officials.
I think, when talking about PLA and government personnel, we should not use the name Muslim but instead their specific ethnic names. Mixing the two concepts was the root cause of that specific member who dragged us into his/her "fight".