It's no different than regular alcohol. Parents that worry about abuse of this form of alcohol are probably already dealing with alcohol abuse issues with their teenage children. Making booze in powdered form and selling it in legal liqour stores is simply another method of delivery nothing more. If a under age drinker can get his hands on the powdered version then getting the regular version is probably not that much different.
In other words, it is irrelevant what format the alcohol takes. If alcohol is available to under age drinkers in your area or if your young people can get their hands on it then they can probably do that regardless of what format the alcohol takes.
Unless you are saying they intend to sell this in regular stores without checking IDs. that's a horse of a different color