Boys 15-24 committing suicide at 4x the rate of girls is not something that has changed much since at least 1975. If anything, the disparity was even greater between 1985-2000:
Meanwhile, the premise of this piece is that social media has increased mental illness for teen girls. Yes, that's self-reported, but it's always been self-reported (and can only be self-reported), so that's not a factor which has changed for boys or girls. So why are girls, but not boys, reporting more mental illness and at greater rates than boys now than they have in the past. That's what this piece is trying to figure out.
Boys also had an increase in self-reported mental illness, so your assumption is wrong. The article is claiming that the increase is larger for girls than boys. However there could be reasons that it's now more acceptable for girls to report mental illness and not for boys, so it doesn't really resolve the sex comparison issue.
BTW the chart you linked shows that we had higher rates in the 1980s than now. It makes the recent increase look like it's just part of a long-term cyclical trend.
https://www.cdc.gov/mmwr/volumes/66/wr/mm6630a6.htm
Meanwhile, the premise of this piece is that social media has increased mental illness for teen girls. Yes, that's self-reported, but it's always been self-reported (and can only be self-reported), so that's not a factor which has changed for boys or girls. So why are girls, but not boys, reporting more mental illness and at greater rates than boys now than they have in the past. That's what this piece is trying to figure out.