Tour level players swing in a consistent rhythm of 3 to 1, backswing to forward swing, and the trend is actually gravitating towards 2.5 to 1 for the modern player’s swing.
Tempo is elapsed time.
A given tempo has two parts, backswing and forward swing. That’s where rhythm comes in. It’s the ratio of time used in the backswing compared to time used in making the forward swing.
That ratio of 3 to 1 applies to elite players past and present – the backswing takes three times longer than the forward swing ( trending to 2.5 to 1 for the modern swing ).
That, of course, doesn’t mean that the backswing is slow, either. It’s only slow in relation to the forward swing – which is like lightning.
Great tempo doesn’t mean a slow swing.
Great tempo is a well-timed swing.