Forcing the order by specifying specific JSL commands your desired outcome can be obtained.
names default to here(1);
dt=open("$sample_data/big class.jmp");
//dt<<color by column(:sex);
ow = Oneway(
Y( :height ),
X( :sex ),
Box Plots( 1 ));
report(ow)[FrameBox(1)] << Row Legend("sex");
ow << histograms(1);
Jim