You know...the Toontrack website doesn't really do a good job of explaining the two options.
If you look at this page:
https://www.toontrack.com/ezkeys-line/
There is the mention of expansion packs, but no real effort to show any distinction between them and full versions.
Then, if you pick any one of the EXKeys pack off that page:
EZkeys Classic Electrics | Toontrack
The full version price comes up, and you would have to know to change the "Product Variant" from "Regular" to "Sound Expansion", and then the price changes...but of course, you don't see it unless you choose it, and you may not choose it, 'cuz you don't see it.
I get a feeling they did that on purpose.
I mean, they could easily have shown both versions and both prices on the page without you having to switch the "Product Variant".
That said...if you scroll all the way down to the second page I posted...there is this comment:
"Already got another EZkeys?
Congratulations, from now on you can purchase any other title at a discount. Log in, find your new EZkeys and select the “Sound Expansion” option before you proceed to checkout."
So it does seem like this was a recent change...again, they could explain that at the top, with the pricing differences both clearly shown.