It seems that the ratio in axes_bounds are relative to fig.axes_size and not to fig.figure_size as specified in the doc
Reported by Calixte DENIZET
f=figure("figure_size",[500,500],"auto_resize","off");
axes=newaxes();axes.axes_bounds=[0,0,0.5,0.5];plot2d();
uicontrol("unit", "pixels", "Position", [0,0,250,250],"String","Hello");