I've not tried every name, but some of the names aren't changing on the standings/race director/results sections. They work fine during the race and on main menues, but as soon as you check the sections I mentioned it shows the original drivers name.nikashi submitted a new resource:
F1 2021 Names and Teams Changer v.0.5 - F1 2021 Names and Teams Changer
Read more about this resource...
Effect drivers I've found so far: Perez, Ocon, Stroll, Tsunoda, Piquet, Sato, Ticktum, Aitken, Ghiotto, Nissany.
And I've also noticed that sometimes Antonio Giovinazzi and Daniel Ricciardo occasionally come up with first name in full capital letters as well, which none of the others suffer from.