These two sentences appear on the same page of an online dictionary.
Possessive pronouns are pronouns that demonstrate ownerships.
Possessive pronouns include my, mine, our, ours, its, his, her, hers, their, theirs, your and yours - all words that demonstrate ownership.
It makes me wonder which form--plural or singular--makes more sense in this situation per se. I would go with plural. I am assuming the rational for the singular use is that the author takes ownership as an abstract concept here. But is this usage common enough to make sense/make the sentence sound natural?
Some more examples, as mentioned in a comment:
Oxford Online Dictionary:
‘Whenever press ownerships have been allowed into commercial television ownership, the situation has been favourable to the emergence of media moguls.’
Wikipedia pages (not Wiktionary):
The company has evolved through several corporate ownerships since its establishment in 1960 in North Carolina.