It works, but why? Leeds is finished leather with a protective top coat AFAIK. On the other hand, if its some unfinished leather/crust leather, it could help.
On the other hand, the effectiveness of water protector really depends on the severity of rain fall expected. They were absolutely useless in monsoons.
I would worry more about the rain if its leather sole; works in light rain, but water will sip into the insole if its heavy enough.
It does have a leather sole. With a topy by now since I had them on in the last rain here and it wasn't so nice. I already sprayed the bit of sole left between the topy and the rubber heel but wanted to wait with the upper. My walnut Leeds looked pretty soaked in and around the toe area and around the welt (walked through grass in a park) and my foot felt damp from below.
The shoes just dried out naturally and are fine obviously but since I'm going on a trip ... don't want to have to put on half dried shoes the next day.