I was confused as my project [0] I called it a git heat map, not realising that a similar term was used for other completely different visualisations

[0] https://github.com/jmforsythe/Git-Heat-Map

Heatmap is one of those terms that gets applied to a few different things, especially choropleths. I've also seen it applied to grids (like a hours of the day vs day of the week, where each cell is how much X happened that hour).

Imo I'd say it's both, since the color is measuring something and not categorizing here.

I always assumed that heatmaps were a type of treemap