As far as the text of the psalms is concerned, we need to recall that the Council met in the aftermath of the disastrous Translation of the Psalter commissioned by Pius XII and authorised by him for use in the divine Office (yet another example of the fact that major errors in the methodology of liturgical reform had already gripped the Latin Church before the Council; the Council was merely one episode in a flawed process which was already under way, and even under some of the same personel). The departure of the Pian psalter from the characteristics of Christian Latin - and this at a time when Christine Mohrmann's researches were still fresh in the minds of learned readers - meant that there was a very widespread unease about it. Tactfully, SC decreed that the "work of revising the psalter, already happily begun, is to be finished as soon as possible, and is to take account of the style of Christian Latin, the liturgical use of psalms, also when sung, and the entire tradition of the Latin Church". Thus the psalter included in the LH can decently claim to have been mandated by the Council, even if one's personal preference would have been to keep the words which had sanctified the lives of latinophone worshippers for a millennium and a half.
As far as the distribution of the psalter is concerned, the Council mandated that the psalms were to be distributed over a longer period than one week. LH, of course, distributed them over four weeks. One may have one's own views about the wisdom of what was done, and the opportunities that were missed of returning to something more traditional. In only one matter, however, is it clear that LH innovated without a conciliar mandate. Into the Psalterium, which by long tradition had included Old Testament canticles in Lauds, were now introduced New Testament canticles at Vespers every day. They were taken from S Paul's purple passages and from the songs of the angels in the Apocalypse (the production of the latter category of canticle required some use of scissors and paste). To introduce without a conciliar mandate a feature which increased the amount of psalmody to be arranged at a time when the reformers were under orders to reduce the burden on the clergy, seems perverse. Objectively, it is another example of the dynamics of a process in which those driving the engine slipped, perhaps even without noticing it themselves, from implementing a mandate, to giving themselves free rein to innovate 'creatively'.