I love the intent and execution behind this. The implication of imprecision in the underlying data through rough looking "hand drawn" charts and graphs is a really smart design hack.
The same approach could be used for mockup apps/websites
Do a high-fidelity, fully realized html mockup, and you're more likely to get feedback about the little details like fonts, colors, icons, spacing, wording and maybe minor tweaks to the layout.
Draw a really low-fidelity mockup with a sharpie or on a whiteboard, and you're more likely to have a good discussion about fundamental layout/concepts, overall approach, etc, without anyone getting hung up bike-shedding about the details.
I think a lot of this has to do with perceived effort: if people think you spent hours building it, they're less likely to suggest a change that would throw most/all of your work out. This doesn't mean you can't or shouldn't prepare ideas/drafts beforehand if you want to, nor that you shouldn't increase the fidelity as you iterate.
I've tried many tools for this, but personally all the best and most fulfilling [early] design discussions I've ever had involved standing around a whiteboard.
There's AvaloniaUI, though, if you're looking for XAML, UI, and cross-platform.
It was inspired by the 'xkcd' matplotlib theme, which itself is delightful: https://matplotlib.org/xkcd/examples/showcase/xkcd.html