As per the GISS recommendations, all the business units who are using Azure APIM are mandated to be on premium SKU in PRD and UAT environments.
There are many small and medium business units in Sodexo who does not have enough usage (number of APIs) to justify that much cost. So it makes sense that such business units can share resources to reduce the cost.
Global Shared APIM was envisaged on that concept. It uses premium SKU in UAT and PRD environments. This is a GISS approved product as it follows all the security best practices as mentioned at this GISS link. Global Shared APIM charges nominal fee every Quarter for all the premium services. It follows T-shirt size pricing model as mentioned below.