For the RZ67 and the RZ67 Pro II, the battery specifications in the manuals did not include lithium batteries. It may be that before the Pro IID, the website specifications recommended against them.
With the Pro IID, lithium batteries are recommended in the manual (actually in two different places). It may be, however, that when the website specifications were changed to list the Pro IID instead, that part wasn't updated.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2