SC, in Article 93, mandated that "the hymns, as far as seems expedient, are to be restored to their original (pristinam) form, those things being removed or changed which have a flavour of mythology or offend Christian piety. Also, as may be opportune, other hymns should be received which are found in the treasury of hymns".
The first part of this reform was long overdue. Urban VIII had ordered the correction or even total rewriting of the Breviary hymns so as to make them fit the canons of Augustan, classical, Latin poetry. The restoration of the original texts was one of the unambiguously good results of a conciliar mandate. It has the result that, as far as English translations are concerned, those done by Tractarian Anglican Catholics, who were rendering the texts found in the Sarum and other medieval breviaries, are much closer to the texts now restored in the LH than are the translations done by nineteenth century Roman Catholics such as Fr Caswall - who felt obliged to translate the Barberini texts.
In 1968, Dom Anselmo Lentini published an interim set of "Hymni instaurandi Breviarii Romani". One can quibble about details; I think he rather overdid the Reception of Other Hymns, providing whole sets of alternative cycles (recovered, indeed, from traditional sources) to sit beside the old hymns. But I think a fair general verdict would be that he did as he had been told. For a couple of decades, as I said the Prayer Book Divine Office, I used the hymns in this interim collection, and was generally satisfied with it. In particular, it is attractive not to have to read at Mattins a hymn which is a duplication of one appointed elsewhere in the same festal office.
However, the increasing radicalisation of the 'reform' process had shown itself by the time LH was published in 1971. Most notably, a new composition had been provided for the Lauds of each apostle. I wonder if I am the only one to find that the hymns in the Commons, particularly for Pastors, are not of sufficient merit to stand their constant repetition.
But, generally, Lentini* provided the most scholarly and traditional element in the new Office Books, and one that should influence any new edition of the old Breviary.
*Rubricarius, in his comment below, is quite right. He usually is. Sometimes to aid singability, texts were changed by the Lentini coetus. The worst example is Ad coenam agni providi, which in the original is extraordinarily jerky. Lentini smoothed it out line by line. A shame; I think the original rhythmic effects are intentional and poetic. A lesser example is in Venatius Fortunatus. "ferre pretium saeculi" is a syllable too many; it is revised to "ferre saecli pretium". But we should remember that Latin was still a vernacular for VF and he undoubtedly pronounced "pretium" as "pretsum". [Elsewhere, "oculi" is deemed to have an excessive syllable; but it was probably pronounced "ocyi"; compare modern Italian.]
My point was to "pass" a general verdict, and I think it would be unfair to pass a negative one. But of course, we none of us would have done this revision in exactly the same way.
The answer to Albertus' query is that Dom Lentini's chums, like Albertus, felt that ne polluantur corpora "excultis nostris moribus non opportuna est, unde expunctam velimus". In its place they brought in two stanzas from a sixth century hymn in the Regula Caesarii Christe, precamur, adnue. Lentini kept the opening stanza from Te lucis because, being an Eyetie, he deemed it "ab ipso Alagherio quodammodo consecratam". Personally, I'm not too certain about our age being ethically so much more sophisticated than earlier Christian centuries. My instinct would have been to offer both hymns in their uncorrupted integrity as options. But you don't need to explain to me the problems about "option" liturgy.