Works:

Project {
    property string prop: "bla"

    Profile {
        someModule.property: project.prop
    }
}

Does not work:

Project {
    property string prop: probe.prop

    Probe {
        id: probe
        property string prop
        configure: {
            prop = "bla";
            found = true;
        }
    }

    Profile {
        someModule.property: project.prop
    }
}

In the second example, the value of prop is undefined. The documentation doesn't explicitly specify when and how Profile items are evaluated, But I would assume that Profile items get evaluated after the project is flattened, at least, after all properties of the surrounding Project item are resolved. That includes probe execution.

Evaluating Profile items before Project items makes less sense to me, because it is not possible to access module properties from within Project items.

I would furthermore expect that accessing probe from anywhere in the current file would work as well.