It doesn’t seem like a bug, it’s how feather icons scale the stroke vs how Figma scales (different implementation).
In feather icons the stroke-width is relative to width and height of the object (notice viewBox is still 24x24px!). In Figma to achieve the same result, one would have to use the scale tool and resize the icon to the desired value. In Figma however all three properties will be scaled too: viewBox, width, height and stroke-width.
Here I am copying the svg code, directly from feather icons app (website) - notice size 92px and stroke-width: 2