You're severely underestimating the complexity of choice-based games. Ink, for example, is Turing-complete (it features variables, looping and branching. (As is your description of "fancy CYOA books," for that matter--take the PDF as the rule system and the "little notebook" as the tape.)

I recently wrote an Ink-based game that, among other things, allows you to swap out one of the main characters based on an early choice, necessitating swapping out names, pronouns, behavior and dialogue throughout. You could manage this as a PDF, but you're looking at an exponential explosion in length. Much easier to handle it with variables, subroutines and text substitution.

>Ink, for example, is Turing-complete

So it's PostScript. But, could you get a game with the same playability and freedom such as Adventure?

I mean, roaming around and using objects tryung stuff without being annoyed because of the interface as it happens with hiperlink based games.

Because doing that with if6 is dumb easy, you can create better stories with a much higher interactivity and emergent gameplay.

On games written with Ink, most games I've seen are as "complex" as the Lone Wolf adaptations for Android.

https://projectaon.org/staff/toni/

"Interface" is exactly the right word. You're never going to capture the feel of a parser-based game with a choice-based engine because the input is so limited. But don't mistake the limitations of the UI for the potential complexity of the underlying game.

That said, if you remember games like The Secret of Monkey Island, they attempted to capture the feel of a traditional text adventure, but they swapped out the parser for a visual interface with a limited vocabulary. I've seen at least one attempt to do something similar with Twine (a traditionally choice-based engine).

Some of the qualities of parser-based IF that make it most distinct from choice-based IF are also the most controversial ones: "freedom to explore and discover" can also be rephrased as "requirement to repeatedly play guess-the-verb". More accessible parser-based IF tends to provide affordances that make it feel closer to choice-based. A really well done, detailed, thoughtful parser-based IF can have a wonderful fluency and immediacy that choice-based IF has trouble replicating, but well done, detailed, thoughtful choice-based IF can provide a degree of narrative focus and clarity that would feel weird and railroad-y with a parser.

>requirement to repeatedly play guess-the-verb".

Not so much since mid-90's. That happened with GAC/PAWS/DAAD games for the ZX Spectrum, yes, but since Inform (specially inform6) targetting the ZMachine with the English library for i6 it made dumb easy to generate basic actions and synonyms to avoid that from the roots.