They are floating point values. There is going to be some slight drift because you can't store those exact values in a float, only a very close approximation. Anything that rounds it to a couple of decimal places is going to get the original value back in almost every case.

Yes, I understand that ...

After cheking the data, for example if "assembling-machine-3" has a defined collision box in \data\base\prototypes\entity\entities.lua as:

collision_box = {{-1.2, -1.2}, {1.2, 1.2}},

And the output in data-raw-dump.json is:

"collision_box":
[
[
-1 ...

The output of --dump-data for some values has an excesive number of decimal places. Examples:

clickable_label = {
type = "label_style",
hovered_font_color = { 1, 0.74000000000000003552713678800500929355621337890625, 0.4 },
clicked_font_color = {
["r"] = 0 ...