Yes. The flash zoom setting affects how much of the umbrella is illuminated, which changes how large the umbrella acts as a light source.

A wider zoom fills more of the umbrella, usually giving broader, softer light. A narrower zoom lights less of the umbrella, so the effective source is smaller and the light is less softened. That usually doesn’t create an obvious hotspot on the subject, but it can reduce the umbrella’s softening effect.

Flash position matters too. If the flash is too close to the umbrella, the beam may not cover the whole surface, so the outer edges are wasted. Moving the flash farther back helps fill the umbrella more completely, but it also costs power and puts more stress on the shaft.

If you zoom too wide, some light may miss the umbrella and spill onto the background or subject.

So the practical answer is: use zoom and flash position together. Wider zoom plus proper placement usually gives the most even umbrella fill; narrower zoom can be useful if you want a slightly smaller effective source or less spill. A little testing with your specific umbrella and flash will show the best setup.