Blessing of an engaged couple

In Paul Turner's Blog by Paul Turner

Q: Both the Order of Celebrating Matrimony (221) and the Book of Blessings (198) state that the Blessing of an Engaged Couple should not take place during the celebration of Mass.  

In your book, Inseparable Love, your commentary explains that the blessing should not be combined with a wedding, but says nothing about Mass.

What is the reason behind the prohibition of this blessing being celebrated during Mass?

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A: The first edition of the OCM did not include this blessing, so its first appearance was in the Book of Blessings. The second edition of the OCM copied the information from there.

I’m not sure why the Book of Blessings forbids the blessing of an engaged couple from taking place during Mass, but in general it provides a limited number of blessings situated within Mass. Presumably for a totally different reason, for example, the blessing of farm animals takes place outside Mass. So does the blessing of buildings such as a library. For engaged couples, I suspect the concern is that no one confuse the engagement with the wedding, and its separation from Mass shows in one small way that engagement does not rank with the sacrament.