A daunting prospect!: It's like eating an elephant: one bite at the time and you'll get there .
For the total number of strings: You have to select "Standard" for a standaard Moodle installation. The core file alone is a very small subset of the strings (no plugins, no error messages, privacy strings, ...) . Selecting "Standard" today, gives you 29533 strings in 491 files, not 1 file.
As for the screenshot: yes, some details of the interface have changed since the last overhaul of the language tool. The screenshots need updating.