why are spaces allowed in the map name but not folder or feature layer names?
some links in this thread.
Solved: ArcGIS Pro Project - Naming Conventions? - Esri Community
Windows stuff Naming Files, Paths, and Namespaces - Win32 apps | Microsoft Docs
There are many links for folder and filename information. "Map" names are governed by esri rules.
Agreed, asking for a world of hurt allowing spaces.