3 degrees is the generic "I don't care and don't want to worry about it" draft angle. In many cases 0.5 degrees of draft angle is a non-issue.

3 degrees on a lego brick would be a difference of .3mm over its height. For comparison an amoeba is about .5mm. If you're zoomed out enough that you can see the length, you're not going to be able to discern the angle. The only way you'd see it is to check for the gap between the wall and a precision square.