@exaltbass This is all US-specific, since you mentioned the AAP.
My understanding is that floor beds aren’t manufactured to comply with the safety standards that cribs and toddler beds and PNPs have to meet, so they’re not recommended for kids under age 2. After age 2, though, ANY adult bedding is considered safe, and kids can pretty much sleep wherever. So an untested floor bed would be considered just as safe as any other bed at that point.
It’s not so much that floor beds pose a specific danger which is different from the danger posed by other kinds of adult beds - it’s just that they haven’t been designed or tested to ensure that an infant or small toddler can’t get injured or entrapped in them, or suffocate on them, like a regulated sleep space has. So, if you choose to put a kid under 2 in a floor bed rather than a regulated sleep space, then you’re taking a risk - just like you would with bedsharing, letting them sleep in a swing, putting them in a twin bed, etc.
However, a crib mattress on the floor is perfectly safe (and some parents have to do that if they have a child who is too large for a crib, but too young for a toddler bed). So if you want to eliminate the risks posed by unregulated sleep spaces, then you could just put the crib mattress you have on the floor for now, and then upgrade to a floor bed at age 2.
I’m guessing that since a lot of floor beds are also either DIYed or made by very small companies (like Etsy sellers or local carpenters), that there may be an added level of risk there, as opposed to buying from a larger manufacturer. But I don’t know for sure,