I don't think this 'issue' has changed since 'the beginning'.
Names given to the right of the vertical slash are extinct names, common names or accepted synonyms. Either way ONLY the name LEFT of the slash will appear in the Scientific name (you can DELETE the common name if it doesn't apply)
But where you choose a species name, the common name (in Brackets) is carried to the Common Name Panel
You can try this - to Water Cress (but still safely delete the Common name) Substituting A Cress should be OK,
I really don't think this has changed in years but lately the ID panels are more sensitive to (MY) 'interference'.
Take a moment to look at the SANBI Dropdown where several Common names're available in different languages. Should the UK one have Gàidhlig, Gaeilge nah Eireann, Cymraeg version and perhaps regional ones too?
Please, please don't say yes!!