Let me rephrase what I already said more thoroughly; sparring with head shots even at light contact will still be better than not sparring with head punches at all. The advantage of Knockdown karate is the very tough conditioning and being able to both absorb full contact shots but also deliver strikes with a lot of power behind it and technique designed to inflct damage / finish the opponent. Having said that, it doesn't help at all with head defence and the fighting range doesn't really work in a full contact fight with head punches, and this is where the point scoring guys have more of an advantage; with footwork, distance management and also being used to having someone trying to hit their face with a punch.
How do I know this? I actually come from 5 years of Shotokan and point scoring competition before turning to Kyokushin and fighting in Knockdown rules in my early 20's for also about 5 years, until I switched to Muay Thai. So I know a thing or two about both styles and what were real benefits gained from those arts as well as bad habits.
You're not going to impose the same range of fighting as in Knockdown fights just because you're better than your opponent, simply because you can't stand head to head with someone when head punches are allowed, let alone bare knuckle, unless you're basically trying to go into brawl mode to either KO or be KO'd. Most of the time guys in that range would just clinch you anyway.