Details on the preparation of Communion from the Cup:
[105.] If one chalice is not sufficient for Communion to be distributed under both kinds to the Priest concelebrants or Christ’s faithful, there is no reason why the Priest celebrant should not use several chalices.[Cf. GIRM 207 and 285a]For it is to be remembered that all Priests in celebrating Holy Mass are bound to receive Communion under both kinds. It is praiseworthy, by reason of the sign value, to use a main chalice of larger dimensions, together with smaller chalices.
An awkward point for the CDWDS to defend:
[106.] However, the pouring of the Blood of Christ after the consecration from one vessel to another is completely to be avoided, lest anything should happen that would be to the detriment of so great a mystery. Never to be used for containing the Blood of the Lord are flagons, bowls, or other vessels that are not fully in accord with the established norms.
This is the source of the modification that wine be poured into different vessels before consecration. It rather overlooks the possibility that individual altar bread and perhaps even crumbs might be spilled.
My sense is that the CDWDS largely lacked experience with this form of Communion and declined to consult people who did. Great care is needed for good liturgy, and for reverent handling of the elements, before and after consecration. These matter are better communicated with positive examples, rather than less mindful shalt-not’s.