If you find it helpful at all.... I think that many long term mono couples that open up often feel a sort of desire to "protect" their partners. Especially men given our culture. While many will often say that they trust their partners, etc. etc. I have heard many a "but I just want to make sure that my partner is safe because we don't know this person!"
While I think that this idea is often intended to not be malicious or controlling or anything of that sort, I believe that it stems from the fact that we automatically look at people in a complete different light when the potential for dating or sex or romance comes into play. Someone would likely never feel like they needed to vet every new stranger that their partner met on the street. If I'm out at a bar with my friends, I may meet all sorts of random people, some of those people might even be eyeing me up and wanting to talk to me because they like the way I look and want to score a date. Or some of them may just be random people who are out looking to socialize. But if you were out on your own in any other context outside of a date and ended up meeting a new person, would your partner feel like they needed to vet that person? Unlikely. So what has changed other than you know, up front, that the person you're talking to is interested in a possible sexual/romantic connection? Nothing really. But ANY stranger you meet in life might have those same interests.
Basically, I tend to try to ask myself in MANY situations, if sex/romance wasn't involved, would I still behave the same way? Because in many cases, how I treat people, who I trust, how I decide one course of action over another, often wouldn't be different. If I think someone is doing something uncool, I think that whether sex is involved or not. If I think someone did a nice thing for me, it's true whether we're dating or not. If someone cancelled on me, I have feelings about that whether we're a couple or not. Etc. So to me, same applies for meeting new people. I'm capable of making my own determination as to whether a new person I'm going to be meeting is safe, or seems interesting, or like I'd enjoy conversation with them without the help of someone else. And I'm capable of assessing whether the situation feels safe without the help of someone else. So I don't really need my partner to help me with those things. What I do need them to do, is trust that I'm a capable adult that can do those things on my own. They may have feels, or worries, or what have you. But often if they stopped and asked those same questions (would I be worried about this if sex wasn't part of the equation?), it would help people to recognize when they're possibly being either over-protective, or crossing a boundary, etc.