I'm assuming we're referring to people who display a consistent pattern of behavior that violates their stated values, or who experience significant stress and unhappiness sticking to a set of values. And of course I'm assuming that we're talking about people who have enough agency to choose to go with or against their values.

If you say you value things, but you act in ways that are opposite to your stated values, or you resent having to stick to your stated values to the point that it substantially affects your wellbeing, then in what way do you value those things? If, say, someone states on the research survey that they value marital fidelity, but regularly engage in infidelity, or greatly resent having to practice fidelity (or both), then the only indication that they value fidelity would be they said so on the survey. If we're defining a person's values as whatever they say they are, then fine, but all that tells you is that some people are lying, or lack self-awareness.

My point is that the logical conclusion of the study isn't "people with conservative sexual values have trouble sticking to them" but rather "conservatives are more likely to lie or be wrong about their sexual values". Lots of people have genuinely conservative sexual values, and are more or less content with them, but there are more sexually unhappy/confused conservatives than other groups. We can speculate on why that's the case, but that's a more descriptive approach to the conclusion, imo.