I've never heard of a fire being started using a magnifyer on any SAK knife. I'm not sure they could make one if they wanted to. That being said it's strictly for seeing things up close. I don't have an old style one so I'm not sure which one is better. Though the new one must be lighter (even if only by a gram)
Although I have heard of SAK magnifiers starting fires, that's something I have never been able to accomplish despite decades of trying. Although I have been able to burn holes through paper and get a wisp of smoke out of fuzz, the only practical use I ever got out of the project was to give unsuspecting friends a spot of heat (then running for my life

). Since then, having grown up a little, I left off trying to burn stuff with the magnifier, but recently I got a few tips about how it could be done and may yet make another attempt. If it works, I'll post the recipe.
Honestly, the SAK magnifier is not worth it. Get a loupe. Bausch and Lomb, for instance, do a great range fro cheap to expensive, all little, all good. And there's Belomo too - an excellent Hastings triplet for very little. It is a bit big though
Those are good suggestions, but the SAK magnifier is more useful than you might think.
Most of my life in photography was spent with film. Although I did all my
B&W processing, my color slides and negatives were done by professional photofinishers in the area. Before ordering prints or doing anything else with them, I had to examine the films for sharpness and almost always the loupes provided for customers by the labs were either missing or in use. My Swisschamp magnifier proved to be almost perfect for the purpose, providing clarity close enough to the standards of a dedicated optic. There was no need to clutter my pockets with yet another gadget, so that was the glass of choice when away from my "studio."
Over the years, I have also used the magnifier for examining all manner of tiny stuff. A small loupe might have been more convenient or provide some other benefit, but not all that necessary. Less can be more.