Unexpected SVG output for `\multiline` environment

Using MathJax v4 (node direct method), given a multiline environment:

\begin{multline*}
a \\ b
\end{multline*}

I noticed using the 2 new and useful demo pages for SVG and CHTML the behaviour is different when resizing the browser window— the CHTML version has a fluid width but the SVG version has a fixed width.

I came across this behaviour when using SVG rendering in my project, with abnormally scaled maths here:

I think the problem is I need to tell MathJax what the appropriate line width is, and potentially re-render on window resize.

Would switching to the CHTML renderer solve this issue without having to re-render on resize? Are there any other pros and cons to using the CHTML renderer instead?

Thanks.

Start with the linked SVG and CHTML demo pages and the Node direct method, reproducing the multline* example while resizing the browser window. Compare the SVG and CHTML output and determine whether the reported fixed-width and scaling behavior is expected; the issue does not name repository files or tests.