This tract defines ‘legitimacy’ simply as being a state of reality of being the actual child of a parent.
They’ve redefined legitimacy. Legitimacy has always been to do with whether a child is from a lawful relationship.
As in the hierarchy of meaning it comes first…
born of parents who are not married to each other; born out of wedlock: an illegitimate child.
It is the same in my legal dictionary…
The status of a child whose parents were not lawfully married at the time of the child’s conception
Butterworths Concise Australian Legal Dictionary, 2nd ed, p212.
The Canons your site cites are
Can. 1137 The children conceived or born of a valid or putative marriage are legitimate.
Can. 1138 §1. The father is he whom a lawful marriage indicates unless clear evidence proves the contrary
§2. Children born at least 180 days after the day when the marriage was celebrated or within 300 days from the day of the dissolution of conjugal life are presumed to be legitimate.
vatican.va/archive/ENG1104/__P43.HTM
But by annulment you’re declaring that the marriage never was valid. Your own site thus misses the point about what the issue of legitimacy is. These canons refer to marriage is nullified by an annulment because annulment means no marriage took place.
Frankly your site misses the point. The issue of illegitimacy isn’t whether a parent is the real father/mother of a child, but whether the relationship in which that child was legal. According to church law an annulled ruling means no legal marriage took place.