UPDATED:

An ACM hub cluster can support 3500 SNO managedclusters.  

The requirement is to support all 3500 managedclusters with a single argocd app and the ClusterInstance CRs representing those 3500 managedcluster should be within a single folder.

Old text:

The argocd cluster app can support a max of 300 clusters. As a result to handle 3000 siteconfig CRs, 10 apps are required. These however require 10 folders in git. These 10 folders makes if difficult to write automation around. VerizonFar Edge want a single folder holding all 3000 siteconfig CRs