I asked my mid 30y/o japanese fujoshi friends about the difference between yaoi and shounen ai, and she said yaoi and shounen ai are the same, shounen ai are BL that more focus on younger couple hence the name shounen (young person), and yaoi more mature/general couple (mature here for the age of the characters), they actually not differentiated by if theres a sex scene or not in the manga, shounen ai and yaoi are shoujo romance genre counterpart, she actually laughed at me (on a friendly way) because i confused about this matter haha and she suggest me to call this genre BL instead of yaoi or shounen ai to avoid confusion on mypart haha
I asked my mid 30y/o japanese fujoshi friends about the difference between yaoi and shounen ai, and she said yaoi and shounen ai are the same, shounen ai are BL that more focus on younger couple hence the name shounen (young person), and yaoi more mature/general couple (mature here for the age of the characters), they actually not differentiated by if theres a sex scene or not in the manga, shounen ai and yaoi are shoujo romance genre counterpart, she actually laughed at me (on a friendly way) because i confused about this matter haha and she suggest me to call this genre BL instead of yaoi or shounen ai to avoid confusion on mypart haha