I don’t know why it’s not working. I’ve done some looking at the ACF code and to be honest I’m not 100% sure when the meta boxes for the field groups get added or why there’s a difference between the normal positioning and the side positioning. It looks like they are all added during the admin_head action so it doesn’t look like there should be any reason why remove meta box works in one place but does not work in another. There’s a long chain of functions and hooks that need to be followed in ACF to get there and it’s not very easy to follow in some places. Given enough time I’m sure I could work it out, but since there are easier routes to follow to accomplish what you want to do there’s really no incentive to dig that deep. I’m also sure that the developer would be able to tell us, but he doesn’t really answer general question like this. I’ll mark this topic for his attention, but I can’t say if he’ll answer or not.
