Agreed, it is difficult to read between the lines. So simply taking at face value the OP’s initial question, his choice of posting here on the Traditional thread rather than on Liturgy and Sacraments, and like wise your own responses, I would add just as general discussion:
Must one partake of the Cup? Obviously not!
May one? Of course.
Should one? I suggest that the has Church wisely left that up to each individual, each time one receives and according to individual circumstances and preferences.
Why would one? Here I find the USCCB’s
Norms For The Distribution And Reception Of Holy Communion Under Both Kinds In The Dioceses Of The United States Of America most enlightening:
*20. The Council’s decision to restore Holy Communion under both kinds at the bishop’s discretion took expression in the first edition of the Missale Romanum and enjoys an even more generous application in the third typical edition of the Missale Romanum:
Holy Communion has a fuller form as a sign when it takes place under both kinds. For in this form the sign of the Eucharistic banquet is more clearly evident and clearer expression is given to the divine will by which the new and eternal Covenant is ratified in the Blood of the Lord, as also the connection between the Eucharistic banquet and the eschatological banquet in the Kingdom of the Father.
The General Instruction further states that “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.”*
The full statement can be read here:
usccb.org/prayer-and-worship/the-mass/norms-for-holy-communion-under-both-kinds/