This chant should be merged with 003402. The text is the same, the only difference is invocabit / invocavit
If any small difference occurs in the incipit the chant should be listed separately for search purposes. If such a small modification occurs further in the full text you are right that we don't list it as a separate master chant. That's why we will keep this chant as a variant to 003402.
Thanks! good to know the rule :)