Question: The vertical axis is logarithmic even if it is not defined this way.

Version used MAPLE 2015.2

I use dualaxisplot and want a logarithmic horizontal axis.
I can get the expected graphic using either of these two methods

restart:
with(plots):
dualaxisplot(
  plot(x, x=0..1, color=blue, axis[1]=[mode="log"]),
  plot(1-x, x=0..1, color=red, axis[1]=[mode="log"]),
  gridlines=true
):

dualaxisplot(
  semilogplot(x, x=0..1, color=blue),
  semilogplot(1-x, x=0..1, color=red),
  gridlines=true
):

This worksheet contains my true code
(pink lines correspond to < plot + axis[1]=[mode="log"] > and blue lines to < semilogplot >).
You will see that the vertical axis for the plot declared in second position is logarithmic, whatever the way the logarithmic x-axis is defined. 
DecisionProb.mw

I am unable to find out if I made a mistake (which is likely) or if it is a bug?
Could you please have a look at this code and give me an answer?
Thanks in advance