You get easily into quite deep questions with money... Anyway, there are good reasons to argue that dollar bills owned by central banks are not money - at least in any meaningful sense. To see why, let's assume a central bank prints a bill with value of a googol dollars, that is 10^100 dollars and puts it in the vault. Is there any meaningful way that amount of money has just exploded? Do we see e.g. monetary inflation? No.
The moment when bills become money in meaningful sense is when they end up in circulation. And they end up in circulation, when - you guessed it - central bank lends them to banks. The bills are a liability of a central bank, thus they are a note which says that central bank owes that amount to holder, thus they are debt. Yep, I agree, this is confusing and requires very careful thinking.
The moment when bills become money in meaningful sense is when they end up in circulation. And they end up in circulation, when - you guessed it - central bank lends them to banks. The bills are a liability of a central bank, thus they are a note which says that central bank owes that amount to holder, thus they are debt. Yep, I agree, this is confusing and requires very careful thinking.