What hardware was replaced? If it was the core module then you will loose all your data as it is encrypted to the original.
If it was the core module then the OS would be required to test the phone is working and of course they would use the newest version, they wouldn’t install one with an older security update.
The latest updates are also inclined to resolve some reported problems even though there may be others.
REPLACED PARTS: ELECTRO-MECHANICAL PART (MISCELLANEOUS)
SOFTWARE UPDATE (preventive)
Not much information. Since the phone itself was not impaired and only loading was impossible, I assumed no major intervention. But maybe you’re right, I have no idea what parts can be easily replaced and what can not.