i don't know how it is phrased in the book itself but in Tibetan Buddhism there is no god. And their innovation is far beyond this book (at least the plot summary on wikipedia).
Although there is no God, there are many gods (lha, sometimes translated as deity).
To add to the confusion, the same word is used for the so-called mundane gods like elementals and supramundane gods, i.e. beings who transcended subject-object dychotomy and can manifest also under a form of a god, whatever it may be. An inspiration for Clarke could be the famous Mañjuśrīnāmasamgīti or "Chanting the names of Manjushri".
To add even more confusion, if instead of gods we consider God and identify that being with characteristics such as omnipresence, all-pervasiveness, being beyond ordinary mind and so on - then one could attempt do identify it with the central topic of all Tibetan Buddhist tradition that exists under various names (primordial wisdom, the union of appearance and emptiness, self-existing wisdom and so on).
"asimovfan", would you say the same type of criticism of Asimov's injection of the Cristian God in "the Last question"?
In this story from Clarke, the sentiment you just portrayed is acknowledged, and the point of the whole story.
The two westerners cannot understand not only the grand project being undertaken by the monks, but also what "god" even is to them. Before they can really understand, their project is completed and reality changes.
[1] <https://en.wikipedia.org/wiki/The_Nine_Billion_Names_of_God>