I have heard of organisations like this (not sure if it was this particular one).
It sounds very "earnest" and I'm not sure what net contribution a teenager (i.e., legally, a child) is likely to be able to make to a development project in a country where labour is presumably less hard to find than project management expertise.
I suspect the main benefit for the organisation is the profit margin they make on the accommodation cost. Presumably some percentage of the volunteers totally lose it on day 1 or 2 and spend the rest of the time on their phones, and there's nothing they can do about it.
I would also have a concern about the adults involved. Bluntly, among the many altruists, there are some very dodgy people working in the field for relief agencies. There are both good and bad reasons why someone might be available for a poorly-paid, single-status assignment in a relatively inhospitable place. See the stories of child trafficking rings that always seem to follow UN relief efforts or peacekeeping missions.
It would probably be a real eye-opener in both positive and negative ways for a mature and streetwise teenager with the right mentality, but then so would a few days volunteering at their local food bank.
(Apologies if this all comes across as a bit negative - I'm probably biased, but I have a little bit of experience with people who have worked in the international development sector and it isn't all entirely positive.)