If you use STB instead of CTB, then it makes sense that you would want to have the text of the Dimensions on a specific Layer so that you can assign a different PLOT STYLE to the texts of the Dimension rather than having them in a different color which you cannot control by a STB.
In this way we can have the dimension lines by a thiner plot-style and the dimension texts by a slightly thicker plot-style so that reading is easier.
Please note that if using CTB one can assign a different color to the dimension texts and therefore achieve the same result easily. The same easy approach is not applicable in case of having STB for ploting.
Another manner to approach this matter is through the Object Display. For the time being and as far as I can understand, there is no way to have the text of a dimention printed differently than the dimension lines IF using a STB for ploting.