I was wondering exactly the same. My e-licenser says that I have “Halion Symphonic Orchestra 1.x / VST sound set”.
I downloaded the trail version and ran the installer. It updated the content part and installed the vst3 plugin. I used to be able to access HSO only true Halion SE2 / Halion Sonic 2 / Halion 5. Now I can also get it to load as separate VST3 plugin.
I still have the same amount of sounds available, 110 programs. And the installer size of was the same size of what I had installed previously. I am guessing that the 1250 sounds means samples.
The download size was 5.1 GB, and I read somewhere that the Halion Symphonic Orchestra that was sold years ago was about 27 GB.
It would be nice to get some additional information / clarification.