They do what they can to minimize picking up additional water while waiting to be delivered to users, but the filament turns out to be all sorts of different water contents. Plastic films have varying degrees of water blocking ability. Don’t know about Bambu’s shipping bags but for water infiltration the bags are generally multilayer and thickish. Bambu may or may not use them. At any rate, the spools I’ve tested so far straight from their shipping bags have been 42% humidity and 40% humidity for PETG HF. That number won’t make sense without the method - next paragraph.
You can get a handle on filament water content by doing this but there’s not good guidelines yet. But it still gives a good idea where you are: Print flaws - #14 by MZip