Adding a tangential anecdote.

I asked GPT-5.4 High to draw up an architecture diagram in SVG and left it running. It took over an hour to generate something and had some spacing wrong, things overlapping, etc. I thought it was stuck, but it actually came back with the output.

Then I asked it to make it with HTML and CSS instead, and it made a better output in five seconds (no arrows/lines though).

SVG looks similar to the XML format of spreadsheets. I wonder if LLMs struggle with that?