Craig, It makes no difference what unit it used, as long as it is accurate.  1mg = 1000mcg
Suboxone which is labeled as 2mg could easily have been labeled 2000mcg instead and it would be the same thing. Belbuca 300mcg could have easily been labeled as 0.3mg and it would be the same thing. Think of it this way; It is just as accurate to call something 12 inches as it is to call it a 1 foot.  In actuality, the metric system makes more sense because the units of measure are all consistent. In this country we need to deal with pounds, ounces, cups, quarts, tablespoons, teaspoons, gallons, yards, feet, miles, etc. In the metric system we have 5mL (same as a teaspoonful), 120mL (same as 4 ounces), 1000mL (a little less than a quart), but they are all mL’s, not three different units of measure. You grew up learning a far more complex system and are just used to it. I hope this helps.