One pixel per letter on a 4k screen would be 3840 × 2160 chars at most, so around 8 megabytes if we assume one byte per "character tile" on the screen. I highly doubt Zig would die from this.
If I understand correctly then that's for the number of threads, although I also think that the sudden switch from terminal size back to the topic of threads is confusing so I agree that it's not entirely clear what the connection between the two is - or if there is none, that the structure of the article makes that confusing