IGA - Independent Grocers Australia.
Whilst there are some "groups" of IGA stores, IGA is sort of a generic brand used by a bunch of basically independent stores.
In order to compete, and for economies of scale, they do have some central warehousing and distribution, but no store is forced to use anything (as they are independent). OK, there is some economic incentive, as the volume they contribute affects their pricing etc., but basically, most of them will use the warehousing arrangement for grocery staples, but lots will tend to have their own local arrangements for things like fruit and veg, meat, seafood, eggs, milk etc.
As a result, they can tend to have shorter supply chains - of course, this is not as ""efficient" (cheap) when everything works, but much more resilient when issues arise.
Another factor is that they are not totally reliant on a single delivery vector - so if one delivery doesn't make it due to disruptions, it won't necessarily prevent deliveries of other products. A bit more redundancy in the system.