Unlike other PvP like arsenals, the Shadowlands ones seems to miss the individual weapon contents added to the container, so they currently are not listed as collectible in ATT:

Shadowlands has the following PvP arsenals:

• S1 Kyrian: https://www.wowhead.com/item=201881/arsenal-sinful-gladiators-bastion-weapons
• S1 Night Fae: https://www.wowhead.com/item=201882/arsenal-sinful-gladiators-ardenweald-weapons
• S1 Necrolords: https://www.wowhead.com/item=201880/arsenal-sinful-gladiators-maldraxxus-weapons
• S1 Venthyr: https://www.wowhead.com/item=201879/arsenal-sinful-gladiators-revendreth-weapons
• S1 Aspirant: https://www.wowhead.com/item=201878/arsenal-sinful-aspirants-weapons
• S2 Aspirant: https://www.wowhead.com/item=201877/arsenal-unchained-aspirants-weapons
• S3 & S4 Aspirant: https://www.wowhead.com/item=201875/arsenal-cosmic-aspirants-weapons
• S2: https://www.wowhead.com/item=201876/arsenal-unchained-gladiators-weapons
• S3 & S4: https://www.wowhead.com/item=201873/arsenal-cosmic-gladiators-weapons

On top of that, it seems that the Aspirant PvP vendor lists items for gold and items the vendor no longer sells as the release of Dragonflight: https://www.wowhead.com/npc=164095/purveyor-zokuul

For clarity; I play in Unique mode with all covenants specific contents enabled in ATT: