In Azure AD admin portal you will find things relevant to application configuration :
- Application that use Azure AD for authentication
- Security to create conditional access policy
- Things related to the customization of the portal and so on
So yes you have some information that will be part of both portal (Azure portal & Microsoft 365 Admin Centre) but they don't serve the same purpose.
As indicated by the name the Microsoft 365 Admin Centre will be your main point when you want to administrate Microsoft 365 (Exchange, SharePoint, Teams, OneDrive, the SaaS part if we can say it like that) and the Azure Portal will be your main point to administrate Azure (IaaS & PaaS mainly)
So regarding the Health you have something in the Azure portal but not focused on the SaaS (Service Health) and the billing also but focused on Azure Subscription