Anchors replaced by content on lovelace cards

I’m trying to use anchors to avoid repetition on my Lovelace cards. But after saving the card, anchors seem to be replaced by their content. For instance, create this card on a dashboard:

type: entities
entities:
  - entity: sensor.home_assistant_website
    secondary_info: &sec_info entity-id
  - entity: sensor.home_assistant_website_update_available
    secondary_info: *sec_info

Save it, then edit it again. The code is now:

type: entities
entities:
  - entity: sensor.home_assistant_website
    secondary_info: entity-id
  - entity: sensor.home_assistant_website_update_available
    secondary_info: entity-id

What good are anchors if they’re not persisted? Or have I missed something?