What does "they read something daily in their free time in 2025" actually mean?

I think it means actual books.

I think it excludes forums, discord chats, and general online stuff.

Kids are forced to read more than ever before to interact with their peers. The rise of sites like Web Novel and Royal Road are inspirational. I would guess that there are more "writers" than ever before in history.

The PDF report covers the difference between print and screen reading around page 27, I think their daily reading must be content available in print and screen but it is not clearly defined.

That section does show that 2/3rds of screen reading though is direct messages, social media, and text in video games. Blogs and forums only hit 1/4.

Kids might be forced to read more than ever before, but not all reading is the same, anymore than using a games console and iPad as a kid makes you fully computer literate.