I don’t have Absolute, but My understanding…
If your Absolute key is supported by the new Activation Manager, and you want the libraries listed to work dongle free in the new Sonic 7 player, or the last version of Sonic 3 SE (3.5.10) that was released to work without a dongle (3.5.10 shipped with Cubase 12 and Dorico 4 when those first came out…now it ships with the newer Sonic 7 plugin [VST3 only]), then update the sounds.
(You could backup your entire ProgramData/Steinberg directory for a speedy roll back should that fail/safe be desirable…wouldn’t need to redownload gigs of stuff to roll back [hopefully there will be no need to do such a thing]).
If your Absolute key is old enough that it’s only on the old eLicenser, and/or you are still using Sonic/HALion plugins old enough not to tap into the new Licensing system at all (Everything on the old eLicenser)…then there’s no need to take the library updates at this time.
If your version of Absolute is older, and doesn’t provide a ‘voucher’ to move to the new Licensing system…then you’ll still need the old eLicenser anyway. No need or point to updating the libraries.
If you don’t take the library updates, but do upgrade from any version of Sonic SE to the newer Sonic 7, then your sounds should still work provided the old eLicenser and keys are in place (On a Dongle, or active in the old soft eLicenser if you went that route with your Absolute registration).
I can’t confirm for sure that the updated sounds work in HALion 6/Sonic 2 or earlier since I’ve updated to HALion 7, but my understanding is that they should be fine so long as you have the new Steinberg Activation Manager installed, and your Absolute key is activated (An older Absolute key might ONLY be avilable for the old eLicenser system…but should still work with HSSE 3.5.10 or newer, or Sonic/HALion 7).
I do know that after taking Dorico 4 and Cubase 12 content updates for HSSE, that subset of content did continue to work for me in HALion 6 or Sonic 3 instances (Basic, Artist Pro, Hybrid Synths, Flux, HALion Symphonic Orchestra on the Dorico Key, etc).
It did (and still does) seem a bit laggy on my system opening an instance that is using any of the sounds on the ‘new Licensing scheme’ (Opening the UI for Sonic/HALion…mouse busy cursor spins for 5 to 20 seconds before the UI opens) but everything works and sounds fine otherwise. Back when everything was running off my dongle, HALion opened the UI INSTANTLY. I’ve been told that if I disable my network card it should speed things up, but I haven’t gotten around to trying it (only a big deal when I’m performing live, and need those plugins to open/close INSTANTLY).