It sounds as though there has been some misunderstanding about Hebrew Catholics. Although there may be some who identify with the Hebrew Catholic movement who keep kosher and the Law of Moses, that is not something that is being advocated for by Hebrew Catholics as a movement. There are Evangelical Protestants known as Messianic Jews who believe in keeping kosher and the Law of Moses but they are not Catholics.
The Hebrew Catholics I’ve met are fully in line with Church teaching that observance of the Law of Moses (including Jewish holidays and kosher eating) is no longer binding upon Catholics (Hebrew and Gentile alike) *at all *(cf. Col. 2:13-17). To the extent that Hebrew Catholics I’ve known acknowledge and celebrate the Jewish holidays, for example, the intent has been to respect and maintain their heritage and not to observe a non-existent obligation.
For more information about the beliefs of Hebrew Catholics, I recommend visiting the site of the Association of Hebrew Catholics.