The title misleading. A true “Christian” denomination would not, could not, pray to Allah. Ergo, this Presbyterian group is not “Christian”.
Not the “Allah” of Mohammed, certainly. We aren’t addressing the technicality that the term “Allah” was used, prior to Mohammed, in Arabic translations of the Christian bible. Mohammed stole the term, just like the term “gay” and even “liberal” has been stolen today by respective language thieves.