I have this issue to, and so far can't figure anything out.
I do wonder if it was a mistake that they ever showed up at all, some were buggy, and some didn't work at all for me, but the pianos worked great, and I would love to get them back showing up.
In the meantime I'm pretty sure that all of the actual instrument generators are available in the legacy categories, so you would just need to find out what filters were added to make the patch. (possibly by checking in MainStage)
Caleb_P - if you look in the jam pack categories you should be able to find a consolidated version (without Xtra in the title) of all the instruments that have various styles, (ie. staccato, legato, etc... ) when using them, you can use the modulation wheel on your keyboard to switch between those styles, and the 'Orchestra string' ensemble and sections have two more styles (half and whole step trills) than the 'Modern' string patches did.