Yes, subutex is a 'protagonist ' as well as a partial 'antagonist'. In English this means in practice that if you're experiencing withdrawal symptoms it provides relief and makes you feel better. However, if you're not yet completely in the throes of withdrawal then taking subutex acts like Naxloxone and instantly throws you in the midst of the worst withdrawal youve ever experienced. It's like withdrawal x10... all the symptoms are compressed into one instantaneous experience. It's terrible.
You need to wait at least 16-24 hours or until you're in the full throes of withdrawal before taking subutex.
Subutex also has a longer half life (36 hours) than heroin and arguably is harder to come off.
Your boyfriend had no choice but to take more heroin. It was the only way he could feel better. Next time he needs to wait longer before taking subutex.