I've heard about that with tomatoes, I didn't know how true it was. But considering how bland they are compared to garden tomatoes, there might be something to that. Growing conditions and type of tomatoes might be other considerations.
A fun experiment might be to save the seeds of a store bought tomato and try to grow them.
I actually watched a video where a guy attempted to grow seeds from tomatoes he got on a Subway sandwich. He got pretty far with it, but sadly the plants died before producing anything. It might be something fun to try. Growing from seed is really challenging though. I often just opt to buy the plants. The wind knocked over my green house before anything sprouted, so I was a bit upset this year. The tomato plants I got were from the school PTO plant sale. They weren't too expensive though, and they support the PTO. Plus I volunteered that morning, so I was able to pick out some good ones!
Back to the fast food salads topic, I decided to try an experiment playing around with the food apps on my phone, and hypothetically you could turn any McDonald's or Wendy's sandwich into a "salad." All you need to do is remove the bun, and add extra lettuce and tomato.
The downside to McDonald's though is that they up charge you for this. As if fast food didn't already cost enough!

Now Subway has always offered the option to turn any sandwich into a salad, so that's something to think about.
As far as custom orders go, unless it's a place like Subway where you specifically pick out what goes on it, I've always been kind of sheepish about asking for custom orders. The app allows me to place a custom order without feeling embarrassed. I also have social anxiety, so that doesn't help any. (You wouldn't know it how I can strike a conversation depending on the situation though. XD) I always felt bad if I did custom order something, because I felt like I was A. Making the restaurant do more work and afraid the cashier would feel stressed over it, or B. I was always told not to be picky or complain. You get what you get and don't have a fit, and while that's a new saying I've picked up working in elementary, it's basically what I've been taught growing up. It's just a nice little saying to help kids learn to be grateful for what they get.
But you know, my GP seems concerned about my overall health and well being. And I'm almost 40. It's probably time to start changing some habits. And if that means a Big Mac salad instead of a Big Mac sandwich...I guess it won't be too bad.

On another note, there's several videos online that reveal the "secret" to Big Mac sauce. I tried this one, but I heard 8 teaspoons of white pepper, apparently it's 1/8th teaspoon. Don't make the same mistake I did, unless you like extra peppery Mac Sauce.

I will note though that "Dusseldorf" mustard tastes really good by itself. I don't know if I'll be able to go back to regular mustard now. It's a little hard to find though.
Here's the recipe by the "Fast Food Secrets" guy:
https://www.youtube.com/shorts/q80l0DS0zjs