Ok, first, to get some important things out of the way. Voice surgery, or even voice training isn't ever necessary, or at least, it's not something that someone else gets to tell you is necessary. It can help with dysphoria, and it can help with cis passing and avoiding transphobia, but even then, whether that makes it necessary is an entirely personal decision.
As for why people will tell you that your voice passes as cis? There are several reasons. First and foremost, for people who have known you a long time, they often, honestly just can't tell anymore. Secondly, the whole pressure to cis pass that we push on to members of our community is not a positive thing. Like I said above, it's something that people should be deciding for themselves based on their own needs. And I really feel uncomfortable being part of that pressure. So if someone asked me if their voice cis passes, I'd be very hesitant to answer, because the act of answering itself suggests that cis passing is a goal you should be seeking.
The way to get what you're looking for from people here isn't to ask them if you're cis passing, it's to ask people whose voices you find inspiring how they achieved various things. "How did you voice train? How do you shape your vowels like that? Who did you get VFS through?" etc. You're not putting them on the spot and asking them to assess you and your validity, but asking them questions that can have objective answers, rather than subjective answers loaded with judgement.
Now, with all of that out of the way, I had VFS (in Australia), and whilst it hasn't been perfect, it's been a strong positive for me overall. The thing that got me wasn't my day to day voice. It was androgynous, and people didn't know how to read it, until they knew my name or saw what I looked like. The exception was when I was coughing, sneezing, or cheering/yelling. My voice training did nothing for those things, and I got VFS to help me with them. As a result though, my voice now cis passes, but it's also quieter than it used to be. I can yell at my old volume, but making myself heard in a noisy restaurant, or in a workplace meeting without yelling is pretty much impossible now.
And the other consideration is that VFS isn't a magic bullet. The way to think of it is that it will give you more for less from your existing vocal training. After VFS your training will take you further than you were able to achieve beforehand, which means that training is a worthy goal, whether or not you want VFS, and whether or not your voice can cis pass