/v2/characters endpoint - stat selectable items sometimes missing prefixes

For the characters endpoint, i.e. https://api.guildwars2.com/v2/characters?ids=all&access_token=&lang=en&v=2020-05-23T00:00:00Z , it should be possible to display the prefixes for every stat selectable item.

There are two keys where you might expect to find this information, namely (1) .equipment and (2) .equipment_tabs.

I have one character which has currently equipped an exotic stat selectable item - Bounty Hunter's WvW Chestpiece - https://api.guildwars2.com/v2/items?ids=84890 - and this item has the "stats" key available in both .equipment and .equipment_tabs.
I have another character which has currently equipped another exotic stat selectable item - Warlord's Breastplate - https://api.guildwars2.com/v2/items?ids=78608 - and this item does not receive the "stats" key in either .equipment nor .equipment_tabs.

I can't figure out what the pattern is here - they do have their stats correctly selected ingame...

arenanet / api-cdi