Hi Mayer: on step 16 of the tear down you refer to shows this is a 1.9GHz on the sticker on the memory bracket. Apple only made a 1.9 GHz iMac in a G5 and before I left the University I ordered 18 of these computers and remember the tear down because one came with a DOA hard drive and I had to go in through the front instead of the back and the clips at top were a pain to get reset.
I hope this puts your question to a rest.