I have no explanation for that page. The ration of 50 between the smallest and next largest denomination is strange.
The list of withdrawn coins seems incomplete. The most glaring issue comparing the two pages: There are no current 5 Rupiah cons on the legal tender page but also none withdrawn. I wouldn't cite either page as a source of truth.
Is there any validity to this? I think it's just an error, but I don't know enough myself to be sure.
I am from Indonesia. This is not an error. This 1 rupiah coin actually has not been withdrawn yet and it is still a legal tender. Same with the 1 sen banknote dated 1964. They are retained for the sake of completenss and to ensure that banks could balance their daily sheets into the cents.
I have contacted the official WhatsApp account of Bank Indonesia and they have confirmed to me they are still legal tenders.
Last year, a person asked if the 10,000 rupiah note from 2005 is still legal tender. Bank Indonesia responded with an Instagram post declaring all legal tenders as of 2024. Two of them are the 1 sen banknote of 1964 and 1 rupiah coin of 1970.