IIRC, there was a rumor several years ago that every last piece of film in Lucasfilm’s vaults were being scanned in and catalogued. Perhaps this 19SE is just the tip of the iceberg.
I definitely remember this rumor. IIRC, it came from a talk that someone at Fox was giving regarding their cooperation with Disney’s team post Lucasfilm sale? But that’s (I believe) how we found out about all the original elements and plates, etc. being kept and stored all this time.