Only applied to professions at or below the level at which you currently have that profession? IE, you can boost an enforcer to 50, 100, 150, 199, hell even 220 if you already have a 220 enforcer. However, if you want a 199 crat, and you only have a level 75 crat, then the only option you have would be a level 50 boost for that particular profession.
Can't complain about creating "noob armies" of inexperienced players, and I'm not sure a lot of people would make use of this but I definately would. Just needs a reasonable price and not $60 for a 199 or 220, cause full accounts from other sources tend to be more affordable.