As mentioned in other comments, tracking logic is going to be so negligible at those sizes that it's not even worth talking about - it'd be like 100kb at worst.

The problem is Meta is extremely inefficient in writing mobile apps. They solve many problems by just chucking libraries at them, but those libraries are "jack of all trades" type libraries. They use React which is abysmally large, and tons of their own monolithic garbage.

When you write an app from scratch, you only use the pieces you need. Meta is an absolute monolith with years and years of code that's been added over time and it's easier to just "copy/paste" most stuff they've ever written than to start over.