According to the code and comments, the order between linked stylesheets and the amp-custom style should be preserved, which makes sense, as you'd want to keep CSS ordering intact.

However, the expected output in the spec files does not match this order.

For this input:

https://github.com/ampproject/amp-toolbox/blob/v2.0.0-alpha.6/packages/optimizer/spec/transformers/valid/ReorderHeadTransformer/preserves_amp_custom_style_order/input.html#L7-L9

I would expect the output to have the exact same ordering of the two fonts and the <style amp-custom> tag.

However, the expected_output.html file shows a different order:

https://github.com/ampproject/amp-toolbox/blob/v2.0.0-alpha.6/packages/optimizer/spec/transformers/valid/ReorderHeadTransformer/preserves_amp_custom_style_order/expected_output.html#L7-L8