The Web Demo uses the createrawsendfrom command to create a new asset.
It would be surprising if there was an endian issue in the Web Demo, since it's PHP code that reads JSON structures from the MultiChain API, and doesn't decode transaction content directly.
So the issue is likely to be elsewhere – it's worth uncommenting the two lines in functions.php that include:
echo '<PRE>';
This will show up the JSON requests and responses that are being sent to the MultiChain API.