Is AMP-SCRIPT lowercasing the HTML attributes?

Question

It appears that <amp-script> code lowercases all the dynamically added HTML attributes but that seems to break the viewBox attribute for SVG tags.

For example if you have

document.appendChild('<svg height="100" width="100" viewBox="0 0 10 10"> <circle class="smile" cx="5" cy="5" r="4" stroke-dashoffset="-.5" stroke-dasharray="11.5,13.6327" /> <circle class="eyes" cx="5" cy="5" r="4" stroke-dashoffset="-15.5" stroke-dasharray="0,6.6327,0,17.5" /> </svg>');

But the source that gets appended has

viewbox="0 0 10 10"

Notice that viewbox is lowercased which seems to not work.

Does anyone know if <amp-script> lowercases all attributes?

And how to make viewBox work in <amp-script>

Here's a reference to an old discussion about viewBox being case sensitive https://github.com/sveltejs/svelte/issues/1062

The code builds a svg string then appends to the document.

p.innerHTML = '<svg ...';
                        
document.appendChild(p);