Span element nests unnecessarily

Hi,

I have a heading and paragraph and I want to apply a common style. So I 
open the source view and add a span element containing the heading and 
paragraph:

    <span style="text-align: center">
    <h1>Heading 1</h1>

    <p>Paragraph</p>
    </span>

However, if I edit the document and then save it and re-check the 
source, Amaya has changed this to:

    <h1><span style="text-align: center">Heading 1</span></h1>

    <p><span style="text-align: center">Paragraph</span></p>

Surely this is wrong? Span is supposed to contain multiple elements; now 
if I want to change the style I have to update every opening span tag.

(As an aside the above CSS doesn't work in Amaya).

Is this not supported or am I using Amaya incorrectly?

Thanks,

Leon...