When converting to Gems of Dreams, big green gems are losing their values (Roman numerals), meaning we only get the equivalent mana of a standard green gem.
I agree that the “Big Gem” status should remain from this spell. All other “convert” spells retain the big gem value. I think the problem is that special gems are not configured to allow big gem values.
Big Gems should only be transformed if they are the only remaining valid Gems - but this is intended, only standard gems can become big gems, since they are created by matching other standard gems.
This has been the case with all special gems prior to Gem of Dreams as well.
I’ve seen big Dreams before though, I even got some at the start of battle in chapter 3 (2 x III), and matching them did indeed give me the correct mana - I was able to fill my spells with it straight away.
When 3.0 first launched we were able to create big dreams, and as a result we didn’t lose mana.
Plus, now it makes it much harder to enjoy the bonus of Serpentine 1, as we lose our big greens during conversion.
Other special gems aren’t really comparable here, as they only do one thing regardless of size.