I can understand why all the other things would be listed here, and I would understand if sexuality in general was considered inappropriate for children, but why homosexuality in particular? This is strange to me.

<content_rating type="oars-1.1">
  <content_attribute id="violence-cartoon">none</content_attribute>
  <content_attribute id="violence-fantasy">none</content_attribute>
  <content_attribute id="violence-realistic">none</content_attribute>
  <content_attribute id="violence-bloodshed">none</content_attribute>
  <content_attribute id="violence-sexual">none</content_attribute>
  <content_attribute id="violence-desecration">none</content_attribute>
  <content_attribute id="violence-slavery">none</content_attribute>
  <content_attribute id="violence-worship">none</content_attribute>
  <content_attribute id="drugs-alcohol">none</content_attribute>
  <content_attribute id="drugs-narcotics">none</content_attribute>
  <content_attribute id="drugs-tobacco">none</content_attribute>
  <content_attribute id="sex-nudity">none</content_attribute>
  <content_attribute id="sex-themes">none</content_attribute>

  <!-- this line here -->
  <content_attribute id="sex-homosexuality">none</content_attribute>

  <content_attribute id="sex-prostitution">none</content_attribute>
  <content_attribute id="sex-adultery">none</content_attribute>
  <content_attribute id="sex-appearance">none</content_attribute>
  <content_attribute id="language-profanity">none</content_attribute>
  <content_attribute id="language-humor">none</content_attribute>
  <content_attribute id="language-discrimination">none</content_attribute>
  <content_attribute id="social-chat">none</content_attribute>
  <content_attribute id="social-info">none</content_attribute>
  <content_attribute id="social-audio">none</content_attribute>
  <content_attribute id="social-location">none</content_attribute>
  <content_attribute id="social-contacts">none</content_attribute>
  <content_attribute id="money-purchasing">none</content_attribute>
  <content_attribute id="money-gambling">none</content_attribute>
</content_rating>

EDIT: as one commenter pointed out, an explanation can be found in a commit on the git repo and the tag has been removed.

Rationale
***

Certain attributes in the specification require some explanation as to why they
are present. This list is not exhaustive and may be added to in future.

 * `sex-homosexuality`: As of 2020,
   [various countries](https://www.humandignitytrust.org/lgbt-the-law/map-of-criminalisation/)
   have laws which criminalise lesbian, gay, bisexual or transgender (LGBT)
   people. In order for software and content to be distributed in those
   countries without breaking the law, and possible reprisal, it is necessary to
   be able to tag software and content which contains LGBT references, so that
   it can be hidden in those countries.
   However, in other countries (for example, the EU), discrimination laws
   explicitly prohibit discrimination on the basis of gender or sexuality. So
   while LGBT tagging may be available in OARS data, consumers of that data must
   only apply it in countries where the law requires that.

It is still strange to me that anyone would add this tag to an age ratings service, if it is a legal issue and not related to age appropriacy. Anyway, thanks for all the answers (except for those who failed to stay civil and/or brought up american politics for no reason).