Difference in scale. Very common in new electronics.

If you produce <10k units per year, you are in the "fuck you" category of customers where most companies won't even give you the time of day, much less data sheets under NDAs, design tools, or actual access to their chips at somewhat reasonable prices. Chips that are 5 years old are often fully open. This is especially egregious in the wearables space... (Not saying it is for this phone, per se)

Also older chips use RAM that can actually still be bought because smartphone companies + AI bullshit haven't bought all of the stock for the next 2 years.