Simple. It’s part of the diversity of the Church.
The Latin Church has its own laws and its own instructions and discipline. It’s not necessary to always say “this applies only to the Latin rite.” Those words are always implied.
I would not expect a Byzantine bishop who mentions 4 archangels in a homily to say “the West only recognizes 3 names, so if any Latins are listening, omit Uriel” because he’s speaking to his own congregation.
Quite frankly, the Western half of the Church does not always practice “due diligence” when addressing issues that might differ between the two.
In the Church’s diversity, there are legitimate differences in practice between East and West. This is simply one of them—it’s not any more complicated than that, really.