This is a fairly minor bug. On ./koha-tmpl/intranet-tmpl/prog/en/modules/catalogue/moredetail.tt you need CAN_user_circulate to be able to update the "Bookable" property. However, on ./catalogue/updateitem.pl the permission that is required is circulate_remaining_permissions. CAN_user_circulate means that you have at least 1 circulate subpermission. So you can see the update form, but if you try to do it without circulate_remaining_permissions, it'll show you a login screen. Fortunately, this one is an easy fix.
Of course, I don't think it's the right permission to use here, but we should be consistent.
Actually, it's not just Bookings. It's pretty much everything.
Re-thinking that dependency on bug 29002, although the oldest backports probably have 29002 so maybe it's OK...