Normally when a game has already been classified, depending on the modifications made, they would not have to submit again. Most modifications to a game are generally covered, although there are exceptions where they are required to re-submit for classification.
Considering the ‘new’ Australian classification listing (same file number, different classification number), being listed specifically as ‘No Man’s Sky Beyond’, I can only assume they submitted for classification again. This could have been done just to make sure, generally decided upon by the developers (HG) and/or publishers. In this case, Beyond is listed as ‘Multi Platform’ with the applicant being Sony Computer Entertainment.
Main question this leaves me, is whether they were required to submit a new application due to the modifications made, or if Sony just wanted to ensure all was fine. If you have a look at the ‘covered’ modifications, I don’t really see a reason to re-submit. This leaves me wondering if the changes made are actually a total game-changer (VR for example), or if this is moreso considered to be a ‘new’ title, possibly legally required due to sales of NMS Beyond, instead of downloadable update content only.
I honestly think, the latter has been the main reason for the new application. Sure enough we can expect the update to add a lot of new content, change the way we can play the game (VR), and includes improvements to multiplayer. It will however still be No Man’s Sky as we all know it, without any inherent change to it’s core essentials. Just another ‘modification’, expected to be a big one, but apparently marketed as a ‘separate’ title.
Sources:
Hello Games (Australian Classification Database)
Application Process (Australian Classification)
Modified Computer Games - Legal Changes July 2015
Edit:
At least ‘content complete’ and has been submitted to receive the rating. This doesn’t necessarily mean the update is finished and ready for release of course, but indeed, likely soon enough.