Inconsistent label background transparency, when using "translucencyByDistance" property.

Label background transparency is all over the place, when I use “translucencyByDistance”. Screenshot of 3 labels, which all have different background transparency:


The only actual differences between labels are text and position. Most of the backgrounds will also stay semi-transparent even if you zoom in past the “near” point of the “NearFarScalar”.

Even with the same position, same text, same zoom level, but different padding, transparency can be completely different:

Is that a bug or am I missing something?

Here is link to Sandcastle which I used for these examples. You can change scenario in upper left corner.