System Information
Operating system: Windows-10-10.0.19042-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3070 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 497.29

Blender Version
Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: rBc77597cd0e15

Short description of error
When you have a scene with unused data, aka Orphan Data, save the scene and reopening it without closing Blender, the Orphan Data will be handles as if you would press once on the purge button.
If you would close Blender completely, the Orphan Data will be deleted completely. Seems a bit strange to me that it is handled differently.

Exact steps for others to reproduce the error

1. Create a cube, a new material with a texture assigned
2. Duplicate the cube and press on the 2 next to the material and texture name to make it its own copy with a .001 in the name
3. Delete the cube and go the Orphan Data in the View Layer
4. Save the scene, open a new one and reopen the saved scene and you will see that the Orphan Data is gone as if you would have pressed the purge button once