It may not contain "harmful" silicones but that's debatable. Harmless for plastics for sure but leather, maybe it won't ruin it outright but any sort of silicones will shorten the leather's life. Considering well cared for quality leather can last decades silicone treatments can shorten it to 10-15 years.
Leather that's used a lot will most definitely show faster deterioration when treated with these "less harmful" silicones.
6 years is nothing for decent leather.
This is my leather jacket I use for riding, it's 8 years old and still looks and feels like the day I bought it, except the zippers are actually finally broken in. It is 100% full grain leather, no plastic top coats, no nothing. Just all leather. It's been cleaned with saddle soap every year, treated with nothing but Lexol afterwards, and waterproofed with Johnson Paste Wax.
Some of the really greasy treatments I've seen tend to oversoften leather, in particular Leather Honey when used too much or too often, not good when you depend on the toughness of the leather to protect you. Any silicones will tend to exacerbate the wrinkles and cause the top surface to crack within a few years. Even the "non harmful silicones" when it comes to leather, there are no harmless silicones.
Leather jackets like when I ride will show deterioration much faster when used in leather motorcycle jackets because of all the hours exposed to intense sunlight, baking hot desert heat, freezing cold mountains, constant wind buffeting, bug splatters, bird poop, sweat, rain, and even snow on occasions.
And yet take care of the leather properly and even after 8 years it will still look new.
You might know that I'm a proponent of Armor All for plastics and heck I have tried it with leather too with less than satisfactory results and I'm talking in the very long term. But considering how my riding jacket has withstood so much and still comes out looking like new. I'd rather not risk any silicones when I have had similar jackets deteriorate from Armor All.
And if you think Aerospace 303 is a special different formula, the silicones they use are the exact same MSDS CAS number as Armor All. Just before the reformulation Armor All did include alcohol and propelyne glycol. But so do many leather specific conditioners like Lexol, so you can eliminate those from the list of stuff harmful to leather. But Armor All never included the "harmful silicones" that Aerospace 303 seems to imply in their grouping of characteristics of "the competition"