[holdenc]

This is what happens when you dynamically insert your CSS tag in the head after the DOM loads.

[herpderperator]

If you view the raw data coming from the web server, the link tag containing the stylesheet is already present in the head. Although what you're saying sounds like it can absolutely cause this type of behaviour, I'm not sure if that's what's happening in this case.

[holdenc]

You are correct. I suppose it could be an unreviewed NPM dependency causing this ;)