Lost case of text when using Core.EscapeInvalidTags

Hello!

Let's check following code:

$allowedTagsList = [
            'a',
            'p',
            'div',
        ];

$config = HTMLPurifier_Config::createDefault();
$config->set('Core.EscapeInvalidTags', true);
$config->set('HTML.AllowedElements', $allowedTagsList);
$purifier = new HTMLPurifier($config);
$htmlBody = $purifier->purify($htmlBody);

$htmlBody before purifying
<p>Hello! I want attach following xml:</p><p><someGreatTag>someGreatValue</someGreatTag></p>

Expected after purifying
<p>Hello! I want attach following xml:</p><p>&lt;someGreatTag&gt;someGreatValue&lt;/someGreatTag&gt;</p>

But in reality
<p>Hello! I want attach following xml:</p><p>&lt;somegreattag&gt;someGreatValue&lt;/somegreattag&gt;</p>

So, any denied tag lose capitalization (someGreatTag -> somegreattag)

php 7.4.27
htmlpurifier 4.14.0

Reproduce the behavior with the provided PHP snippet using Core.EscapeInvalidTags and HTML.AllowedElements, then trace how the denied tag is handled during purify(). Done means escaped denied tags retain the original capitalization, such as someGreatTag, while the surrounding allowed HTML remains unchanged.