im sorry if this answer is late for you but i think i have found a legitimate solution which is rather simple AF. this worked for me but im not sure if it will work for everyone. download itunes app on your computer, plug your phone into the pc, and follow the prompts like “trust this device”, etc. click the small iphone icon usually located on the top left. then simply hit on “sync” which should be located on the bottom right. this takes a few moments. as soon as i hit “sync”, the system storage on my new phone went down by 25 gb instantly. i hope this works for everyone here as its very annoying to begin with.