Do you mind quoting your source on that so I can double-check it and add it to my files?
It makes sense that the Latin version might not have had the addendum, since the western Ekklesia tended to keep the Easter date in keeping with Bishop Victor of Rome's decree, while the eastern Ekklesia tended to be Quartodeciman ("Fourteenth-keepers"). In fact, Irenaeus actually had to write a letter rebuking Victor for attempting to excommunicate the eastern churches over the issue (Eusebius, Ecclesiastical History, 5.24.10-18).
Also, how is Constantine's letter rendered in the Latin, and could you again please cite your source?
The following is not found in the latin text, but is found in the greek text :
We also send you the good news of the settlement concerning the holy pasch, namely that in answer to your prayers this question also has been resolved. All the brethren in the East who have hitherto followed the Jewish practice will henceforth observe the custom of the Romans and of yourselves and of all of us who from ancient times have kept Easter together with you. Rejoicing then in these successes and in the common peace and harmony and in the cutting off of all heresy, welcome our fellow minister, your bishop Alexander, with all the greater honour and love. He has made us happy by his presence, and despite his advanced age has undertaken such great labour in order that you too may enjoy peace.
Pray for us all that our decisions may remain secure through almighty God and our lord Jesus Christ in the holy Spirit, to whom is the glory for ever and ever. Amen.
Translation taken from Decrees of the Ecumenical Councils, ed. Norman P. Tanner END OF TEXT
http://www.piar.hu/councils/ecum01.htm