To the OP and no.idea...here is a link to the Sydney RI Consul website where it clearly states the 60 day Tourist Visa is NOT extendable.
https://www.kemlu.go.id/sydney/en/default.aspx
The following is copied from Vancouver RI Consul application for a 60 day Tourist Visa...
[COLOR=#008080]A single entry Tourist Visa is valid if presented within 3 (three) months from the date of issuance. It is given to travelers who intend to stay in Indonesia on holiday/leisure with a maximum stay of 60 (sixty) days[/COLOR]
All 211B visas look the same in the passport, even a single entry Sosbud is stamped 211B but, when scanned, and the original purpose for the visa is identified as a Tourist Visa not requiring sponsorship, an extension may not be available.
This is sometimes overlooked in Bali and thus extensions have been granted....but sometimes they may not.
Hence my expression......dodgy!
Anyway ...best of luck!