[2019] Requiem Mods confirmed to be consumed on Lich vanquish

The Prime Time #266 overview has been updated by the 'Becster, now stating

Post Stream note: Requiem Mods are earned with charges, that are only consumed on a successful vanquishing of a Lich. Repeat Requiem Mods in your collection will eventually go to good use, so getting duplicates won't be disappointing if you are using Requiem Relics to acquire things like Riven Fragments, Weapon Adapters, and more!

Note the wording, as it specifically notes vanquish instead of defeat, meaning that the mods are most likely not consumed if the lich is converted, as indicated by the following note near the bottom of the page.

Weapons do not come with slots, and you always get a custom version to your Lich if you choose to Vanquish. If you choose to Convert, they keep their weapon but can join you in battles."

The mods also won't be consumed upon failure to kill, such as with an incorrect mod pattern. Make of this what you will.

EDIT: Edited for clarification and formatting.