Having said that Communion from the Cup adds the fullness of the sign, we have the obligatory reminder in GIRM 282. It’s always struck me that the attachment to Trent’s approach to receiving the Eucharist is a little too excited, as if people are trying to convince themselves it wasn’t an error, and as insistently as possible, to boot:
282. Sacred pastors should take care to ensure that the faithful who participate in the rite or are present at it, are made aware by the most suitable means possible of the Catholic teaching on the form of Holy Communion as laid down by the Ecumenical Council of Trent. Above all, they should instruct the Christian faithful that the Catholic faith teaches that Christ, whole and entire, and the true Sacrament, is received even under only one species, and hence that as regards the resulting fruits, those who receive under only one species are not deprived of any grace that is necessary for salvation.[Ecumenical Council of Trent, Session XXI, Doctrina de communione sub utraque specie et parvulorum, July 16, 1562, chapters 1-3: Denz-Schön, nos. 1725-1729]
Furthermore, they should teach that the Church, in her administration of the Sacraments, has the power to lay down or alter whatever provisions, apart from the substance of the Sacraments, that she judges to be more readily conducive to reverence for the Sacraments and the good of the recipients, in view of changing conditions, times, and places.[Cf. Ecumenical Council of Trent, Session XXI, Doctrina de communione sub utraque specie et parvulorum, July 16, 1562, chapter 2: Denz-Schön, no. 1728] However, at the same time the faithful should be instructed to participate more readily in this sacred rite, by which the sign of the Eucharistic banquet is made more fully evident.
And there you have it. Taught in 1570. Hasn’t changed. But administration could change for (first) the reverence and (second) the spiritual good of those who receive. Meanwhile, for the moment, the laity should be encouraged to receive under both forms.