Why does the XMLAGG give me a different order than my query even though they have the same ORDER BY?

I can’t figure out how to get my xml in the same order as my query. I tried using CONVERT(file_name, 'US7ASCII') along with LOWER to try to ignore accented characters and uppercase letters which made it better but it is still different.
I also tried to use COLLATE but maybe I just don’t understand how it works or how to use it cause it did absolutely nothing.

So what am I missing? How can I get XMLAGG to give me the same result as the query?

Basic query (without XMLAGG):

Ideally I’d prefer not to have to modify this query unless there isn’t any way to generate the XML with the same order.

SELECT id, file_name
  FROM test_files
 ORDER BY file_name;

Result:

Query to generate XML (with XMLAGG):

NOTE: This is with the CONVERT and LOWER which is the closest I got to the result I want.

SELECT XMLELEMENT("files",
                  XMLAGG(XMLELEMENT("file",
                                    XMLFOREST(id AS "id",
                                              file_name AS "file_name"))
                         ORDER BY LOWER(CONVERT(file_name, 'US7ASCII'))))
  FROM test_files;

Result:

<files>
  <file><id>22</id><file_name>!.ppt</file_name></file>
  <file><id>31</id><file_name>!0.ppt</file_name></file>
  <file><id>11</id><file_name>!é.ppt</file_name></file>
  <file><id>23</id><file_name>_.ppt</file_name></file>
  <file><id>32</id><file_name>_0.ppt</file_name></file>
  <file><id>12</id><file_name>_é.ppt</file_name></file>
  <file><id>4</id> <file_name>doc-01.doc</file_name></file>
  <file><id>5</id> <file_name>Doc-02.doc</file_name></file>
  <file><id>6</id> <file_name>doc-03.doc</file_name></file>
  <file><id>1</id> <file_name>docx-01.docx</file_name></file>
  <file><id>2</id> <file_name>Docx-02.docx</file_name></file>
  <file><id>3</id> <file_name>docx-03.docx</file_name></file>
  <file><id>7</id> <file_name>E .ppt</file_name></file>
  <file><id>8</id> <file_name>e .ppt</file_name></file>
  <file><id>9</id> <file_name>É .ppt</file_name></file>
  <file><id>10</id><file_name>é .ppt</file_name></file>
  <file><id>13</id><file_name>E.ppt</file_name></file>
  <file><id>14</id><file_name>e.ppt</file_name></file>
  <file><id>15</id><file_name>É.ppt</file_name></file>
  <file><id>16</id><file_name>é.ppt</file_name></file>
  <file><id>17</id><file_name>e0.ppt</file_name></file>
  <file><id>18</id><file_name>é0.ppt</file_name></file>
  <file><id>19</id><file_name>pdf-01.pdf</file_name></file>
  <file><id>20</id><file_name>pdf-02.pdf</file_name></file>
  <file><id>21</id><file_name>pdf-03.pdf</file_name></file>
  <file><id>30</id><file_name>ppt-01.ppt</file_name></file>
  <file><id>24</id><file_name>ppt-e .ppt</file_name></file>
  <file><id>25</id><file_name>ppt-é .ppt</file_name></file>
  <file><id>26</id><file_name>ppt-e.ppt</file_name></file>
  <file><id>27</id><file_name>ppt-é.ppt</file_name></file>
  <file><id>28</id><file_name>ppt-e0.ppt</file_name></file>
  <file><id>29</id><file_name>ppt-é0.ppt</file_name></file>
</files>

Update

I manage to get my basic query to give me the same order as the XML query by adding a COLLATE binary_ai in the order by clause. However, I would still prefer not to make any modification to my basic query.

I would also appreciate to have some explanation on why an ORDER BY inside XMLAGG doesn’t behave the same as on a query.