At one time, overnight interest rates used to be adjusted without announcement or explanation – “snugging” was a popular term of the late 1980s. The market would generally take a few days, and the general public considerably longer, to work out what was happening when monetary policy was changing. They usually had to wait longer again for an explanation of why it was changing.
That is no longer the case. These days, central banks say they are moving the interest rate, and say why, very openly. This particular form of transparency was adopted quite early at the RBA, back in 1990, under Bernie Fraser.