Sorry for the late reply from me, I love the magneto, glad you are loving yours too!
As others have mentioned there are 2 main reason, well one main reason and one secondary reason.
1, Good contact. Some Atty's cartos rba's post lengths are different. This can lead to a huge gap between said connected item and the top cap, or more importantly if the post is short, no connection to the pin inside the top cap. This can be disappointing/infuriating depending on the day/if you have nothing else to vape with ha.
So, a floating pin will auto raise/lower its position when the vape container (in whatever form) meets the pin in the top cap, pushing it down until it hits the battery to make a connection. Likewise, it if it is short the battery will push the pin up until it meets your container.
A floating pin, however is different from an adjustable pin. An adjustable pin is one that is threaded, and would require some manual configuration at some point. Either your devices are similar, so you size it to be flush/good connection once and be done, or adjust as needed (typicaly with a flat head screw style).
The secondary top cap that will be released at some point looks to be adjustable 1, and 2, is an Ego style top cap with a juice well. This may or may not be something you would like, so just keep that in mind.
I am NOT advising you do this, as it can break your mod, however there are plenty of videos on how to manually create an adjustable pin for the top cap also. Once top caps for the magneto are more easily found you can easily buy a replacement to create an adjustable pin without fear of being SOL if you break your current one.
Now that thats out of the way, the second point is aesthetics. Many people like flush fittings. Without that adjustable many containers will have a small/large (depending on container) gap between the top cap and bottom of the item. You may or may not care if this happens. If you do, one of the above things may be up your ally. Until then you may need to live with that.
With all of that said. I have had quite a few mechanical mods over the years and this was certainly one of the cheapest from a cost perspective, but one of the best from a pure function/design perspective.
I am in love with the magnetic throw of the switch, and it just works. The telescope has a tiny bit of wobble with larger batteries, but thats fine and hard to get away from on the TS mods. The finish and machining is very very good for this kind of mod/source and again, I cant express enough how much bang for your buck you get with this. It looks simple, and it is simple at the end of the day. This is its biggest strength. It is a solid design, solidly constructed and delivered, and it shows.