Nuke in theory you are right but since the sroud is supose to be designed as Everet said to draw air from the whole radiator...

Experience ( and only ) showed that there are not any issues any way an the fuss of making a new sroud is considerable..

Two possibilitiw for improuvment in my instalation at least would be
a. to possition the fan completely inside the sroud ( as wou can see in the fotos halh of the fan is out and then
b. "close" the gap that is about 1cm between sroud and fan...

but that is a .... future project since there is not an immediate need...