There was some change where the file walker used to have to open all files for reading and read some header, and now it’s sufficient to stat() for file system metadata. But this was a long time ago.
Curiously I can also report that after I recently added some RAM (changed from 2GB to 16GB) to my Storj box (hosting ~13TB of data), the file walker got a decent speed-up. Can’t measure it exactly without log entries though. So maybe in your case it is faster swap space that helps?