Always been like that or bug...?

[Axlrose]

Through the use of the skill Research, an enchanter can take:

One part of the left half of Tasarin's Grimoire page 23 and
One part of the right half of Tasarin's Grimoire page 23

and upon a successful combination, will create the spell Levitate. Since a druid can use this spell, and reviewing the Wiki pages appears to have no difference between the two spells, the druid cannot use this version of the spell - it had ENC(16) only. Though I have not tried yet, it appears if I sell this version to a merchant, then the spell may become available to all classes that can utilize it.

So as the title asks, has this always been this way or is this a minor bug?

Thanks!