In looking into this change, there are some subtle implications to changing the existing method:
1) TerraFormSkin uses Form.getSection() in conjunction with section.indexOf() in the "labelChanged" method. This probably would break badly with the proposed change, and the follow-on changes to "getIndex" and etc. would quickly get to be very confusing.
2) As someone noted this is easy enough to implement in an application by following the parent chain.
So, I would propose adding another method: "Form.getEnclosingSection(Component)" that would do what is requested for when it is needed, but leave the existing method alone.