B) Probably because the selection algorithm picks cards unavailable in packs and aren't of Legendary rarity. This itself would probably be an artifact from when Collectors were of all rarities and didn't have the shiny gold background, as that dotted box around their market profile was the only indicator in the database of their collector status.
It's a mild, irrelevant oversight, boo hoo. Please stop whining about silly details and get back to playing Elo.
Cards that arent in packs are technically considered as collectors,according to UR,so its probably not a glitch.
Am i sure that said cards like dj korps arent eligible to be slotted as rares during their "collector run"? im not sure,but in the past rare cards that have been announced as collectors have been eligible as rare prizes despite the obvious bump up in rank rarity.