I agree the sample size is very small, but I do think it’s enough to show that KK doesn’t inherently produce fighters more capable in full contact.
Kyokushin has a very good track record when it comes to translation to k1 kickboxing with cross training or adaption, way more so than shotokan, wado etc.
In MMA its much closer. Regardless of who has the edge more fighters stand out at the top level as shotokan like stylists than kyokushin like stylists. There are a few possible reasons for this, some may argue that the smaller gloves, takedown precense etc. In mma and karate combat make shotokanised karate more effective with its movement and its greater focus on precise single shots and long, deeper stance
Basically under this argument the more trading elements of knockdown karate translate much better into k1 rules with the larger gloves and different dynamics. The theat of takedowns and the longer stances people stand in to thrawt said takedowns makes it harder to punish the vulnerable elements of the shotokan based wkf style.
However I also think part of the reason kyokushin guys register less is because they don't fit some peoples image of karate and some of the ones who cross train stand out less from a more kickboxing based style than a shotokan style, which is a style that really focuses on some things at the expense of others and looks aesthetically quite distinct in its stance and movement.
There are more kyokushin trained guys in MMA than some people may think tho. Whether they count as having a strong kyokushin base in their current fighting style depends on how you define kyokushin.
Personally I still think there's quite a lot of distinct stuff clearly visibly kyokushin (rather than more universal) that gives an edge in certain areas to practitioners with kk bases in k1 and mma. This is particularly apparent in kickboxing,but you see it in MMA too.
Even Gsp, arguably the mma goat has a kyokushin base and it shows up more than people seem to think in his, admittedly more mma striking based, game. You'll see him kick with kyokushin form on numerous occasions for instance.