Work "for experience" and unpaid/underpaid internships are just different names for worker exploitation. I almost got bamboozled into accepting something like that because I was desperate and to this day I am glad that I didn't. Instead I got a job that adequately compesates me for my time and work.
Sure.. that can be the case. But unpaid internship can easily be worth it.
A company like chucklefish which is small, maybe not a lot of capital flying around, but still has very high visibility... IMO it makes sense that they would offer something like that.
Every entry level gaming industry job this person applies for hence forth, he/she will have a leg up in getting an actual interview. Let alone the industry folks they may have met along the way. Its great to have that before you even finish HS.