Sorry LB but I'm confused

Each end of the oar travels through the arc of a circle and the oar is a simple lever where the rowlock is the fulcrum.

The effort of the rower pulling on the handle acts on the water at the blade end and the force on the water can be altered by the relationship between the two distances between (a) the fulcrum and the grip and (b) the fulcrum and the blade.

The longer (a) is relative to (b), the less the effort to produce a given force on the water.

If, therefore, the length (a) is extended, the hands will overlap, generally when the two oars are co-linear and there are only two options. 1. More propulsive thrust will be generated or 2. less effort will be required for a given thrust.

Even if you consider the water as the fulcrum and assuming zero slippage, the effect is the same.

The overlap is more obvious when a single rower has a pair of oars but the lever principle is the same in all cases.

I think this stacks up.

Tony