i'm trying to understand the following in PDI 5.4.
I have a main transformation, which uses the simple mapping step to execute another transformation.
In the settings of the simple mapping step, i set a parameter with a static string value.

In the subtransformation itself i declare the parameter with no default value.
Then i have a get variables step to get the parameter and after that a logging step to see the value of the parameter.

The static value i set in the parameter tab is NOT shown on the logging. The same when i use the 'normal' sub mapping step.

We found that the option: [Inherit all variables from the parent transformation] must be UNSET in order for above example to work. Which is weird, because inherit means the all variables INCLUDING the one you're setting now, will be passed.

From the [HELP] we're not getting any wiser:
Inherit all variables from the parent transformation: If this option is checked, all variables available in the parent transformation will be available in the sub-transformation, even if they are not explicitly specified in the Parameters tab. 
IMPORTANT!! : Only those variables/values that are specified are passed down to the sub-transformation.
Can anyone help me to understand this? Is this a bug, or am i missing something?