I have found either a possible source of this claim or an alternative interpretation to the one presented in that statement of that Wikipedia article (as I understand the statement anyway).
Episode 46 of the YouTube series Mental Floss is entitled "Misconceptions About Mythology" and lists 10 apparent misunderstood points of (exclusively Greek and, by extension, Roman) mythology. All of them look good to me except, incidentally, the one in question, which is the list's Number 3. This item makes, near as I can tell, an inaccurate "correction" of the "misconception" that there was in any sense a definitive list of Twelve Olympians.
It lists all the deities you are asking about in exactly the same order but makes a slightly different claim about them, which may only be grammatical, but which nonetheless, therefore, differs from the meaning of the Wikipedia page.
Here is a transcription of the video presentation, from the Mental Floss website1:
If I am reading that aright, it is saying that there are a number of ancient Greek texts containing lists of the Olympian Dodekatheon which swap out some of the names of "the Big Twelve" who are commonly known to have been "canonical" members of the group with one or more among Hebe, Helios, Selene, Eos, Eros and Persephone. But there is no reference that I could find to which texts these might be or what the list of the Twelve should look like in these alternate versions, nor how many of the "usual" members would still be present therein.
My theory about how Wikipedia ended up with its version of this is that someone watched the aforementioned web series episode or read its transcription and then, in the process of editing the information into the Wikipedia article, the point mutated into saying that the listed deities regarding whom you are asking sometimes occurred together in a different group of twelve divinities. This is not the same thing being meant by Mental Floss.
A clue that I might be mistaken about Mental Floss being the origin of this (accurate or inaccurate) information is that the Internet series episode was published in late 2015 while the editing of that portion of the Wikipedia article seems to have taken place (and been discussed/debated) at the beginning of 2008, rendering it unlikely that the former comes from the latter. The construction of the sentence by Mental Floss, however, I find to be less ambiguous, which thus makes it appear to be more authoritative (for whatever that is worth).
Beyond all that, I can see how some of the deities in question fit together, but I am unaware of any ancient source that might link not only all the six mentioned, but which groups them together with six others, whichever those ones might be.
Helios, Selene and Eos are siblings and are among the cosmic lights of the sky: Sun, Moon and Dawn respectively. Both Selene and Persephone occur, among others, as night-goddesses, and there are some associations between them and Hebe and Eros, maybe also Eos. But putting them all together in a special class of their own seems quite random, which is why it would make more sense to me that the Mental Floss quote is the original form of this listing, which was not intending to create a new group of twelve gods but was rather stating that these six were sometimes members of the Dodekatheon.
1. An alternate link to both the YouTube video and a transcription thereof may be found on Nerdfighteria Wiki.