diaeresis (plural diaereses)
1. (orthography) A diacritic ( ¨ ) placed over a vowel letter (especially the second of two consecutive ones) indicating that it is sounded separately, usually forming a distinct syllable, as in the English words naïve, Noël and Brontë, the French haïr and the Dutch ruïne.
It makes perfect sense to use the diacritic in this way and it is part of their style guide, has been for some time.
You couldn't even spend the time researching what you're complaining about. Talk about pretension.