c) per se Laudes recitari debent horis matutinis, Vesperae autem horis vespertinis prout ipsa nomina denotant;
The questions is whether ipsa nomina denotant refers only to the horis Vesperae or also to Laudes. Already in Classical Latin vesper denotes the evening. But the etymology of "Lauds" (laudate) does not seem to refer to a particular moment of the day. The name of this liturgical hour seems to come from some psalms. As Wikipedia states:
The name is derived from the three last psalms of the psalter (148, 149, 150), the Laudate psalms, which in former versions of the Lauds of the Roman Rite occurred every day, and in all of which the word laudate is repeated frequently. At first, the word "Lauds" designated only the end, that is to say, these three psalms. Little by little the title Lauds was applied to the whole office, and supplanted the name of Matins, which in turn was reserved to the night office and replaced the name "Vigil".
So, it might seem that the phrase ipsa nomina denotant refers only to the Vespers. However, the Spanish translation of the above document states:
c) De suyo los Laudes deben recitarse en las horas de la mañana y la Vísperas en las horas del atardecer, como lo indican los nombres de estas partes del Oficio.
I couldn't find another official translation, but there is an English translation, made by a [seemingly non native Spanish-speaker] priest and academic, with the same result:
Morning Prayer (Lauds) should be recited during the morning hours and Evening Prayer (Vespers) during the evening hours, as the names of these parts of the Office indicate.
The emphasis in both translations is to remark that the plural is referring to both hours. So, are these translations wrong? Or does perhaps laudate imply morning hours? (Or maybe translations are right and the Vatican document is wrong?)