It looks like I was able to use testdisk to recover the partition table: I got back the same volume name, so I was super happy.. But sadly I opened the volume and it's empty

I noticed from right-clicking and clicking "get info" that I get "Capacity: 2TB, Available: 2 TB (144 KB purgeable)"
1) Why was possible to recover just the name and not the files?

2) What does tre message "144 KB purgeable" mean?
3) I was reading that some people had to change the block size from 512 to 4096 when using 2TB hard drives, should I do it?