This kind of stuff is becoming standard practice in the sports industry, there is a history of using DXA (DEXA) scans for monitoring body composition in speed and power athletes:
https://simplifaster.com/articles/tracking-body-composition-athletes/
Even the National Strength and Conditioning Association recommends monitoring body composition in athletes now:
https://www.nsca.com/education/articles/kinetic-select/sport-performance-and-body-composition/
The research has been clear, extra weight can really hurt sports performance: a 2% increase in weight can increase 40 yards dash time by .26 seconds and decrease vertical jump heights by 2 inches. The application to track and field sprinters and jumpers is pretty clear:
https://pubmed.ncbi.nlm.nih.gov/21448047/
So the question is, is there any way for a coach to handle this subject and present this information in a way that is sensitive and supportive, but still gets the message across?