You are assuming everyone is of the same opinion as that particular group. You should know better really, much as you are implying there are no muslims in Bali, c'mon.
I am aware that many Muslims do not necessarily follow every fatwa from MUI. I also have not implied there are no Muslims in Bali.
However, I believe the rejection rate will be high among Muslims, especially since a viable alternative (Sinovac) is available. I am not making this statement lightly, but basing it on precedent with the MR vaccine (Rubella) which received the same ruling from MUI. This has led to rejections all over Indonesia, for example in Palembang, where only 52% of children were allowed by their parents to be immunized. Can you imagine the wastage and disruption if the AZ vaccine is rejected at that rate? Or generously, even half that?
In the case of a scarce product that is also highly perishable such as a vaccine, the government has a moral obligation to ensure that the rejection rate is as low as possible. One way it can do this is by allocating them to regions that have a fewer percentage of Muslims, while using the Sinovac vaccine, which has MUI's full endorsement, elsewhere. I don't see how this can be construed as "nasty" unless you're implying that the Balinese are less deserving of a vaccine, and I'm sure that is not what you meant.