The print-material tag clearly states that it is different from material:
Print-material, in comparison to the tag 'material', helps to specify that the question is concerned with the material the print itself is made from. This includes 'filament' as a subgroup but also SLS polymers for example.
Where as material states, more or less, the same thing:
For questions about compatible 3D printing materials.
For questions regarding 3D printable materials such as whether a material is capable of being 3D printed, optimal 3D printing parameters (ie. extrusion temp), mechanical properties of materials, etc.
To me, even though print-material states that it differs from material, I can't really see the difference, unless material is a superset of print-material, and not only confined to being printed, but also construction of a printer (i.e. acrylic, wood, steel, aluminium, etc.). If the latter, then the description of material is a bit misleading and may require expansion.
Can someone explain?