Not output Mythic Rare Card From API /sets/<code>/booster

[Idenon]

Hi.
When I developed application with Magic: the Gathering API, I have notice this issue.
API /set/[code]/booster don't output Mythic Rare on JSON.

Attached File is this example. It's RIX output.
You search words 'colors', then you can know here is only 13 cards. Originally, should be 15 cards.
I was tring several times, if this API output Rare, here is 14 cards.
(I think, this is also fewer, but I don't have Idea of this issue.)

Please resolve this issue.
I'm cheering you.

best Regard

example_RIX_booster.txt

[Idenon]

Addition, I have find this issue on WAR, MH1 too.