When attempting to add IP addresses to the custom allow list, they need to be done one at a time, which is a lengthy process and clutters the custom list. While wildcards can be used, that is not specific enough and does not allow for identifying specific ranges.
The custom allow list also only allows the IP through if it is directly being requested - it does not help if a domain is what is requested that uses said IP.
There should be a better way to define a range of IP addresses to always allow through.