He says "a teen". It's just incorrect grammar. He could have said 'his or her heart' or 'their heart', but not every teen is a 'he'.
The shift to treating he/him/his as exclusively male seems to be a fairly recent phenomenon (last few decades) as American social progressives sought to change language to be explicitly-inclusive instead of implicitly-inclusive and to avoid confusion due to the context-dependent dual meaning of such words.
1970s - "he" means everyone 1990s - "he/she" means everyone 2020s - "they" means everyone
as is well studies, we know very concretely how language and word usage influences thought (because it is thought, expressed)
Kind of a wild take to ignore centuries of implicit and explicit exclusion of women from having civil rights.