As an update, I tested a 100% stock ShooterGame with zero changes on a fresh LyraStarterGame project.
Modifying B_Hero_ShooterMannequin to early-out of the AddInitialInventory BP function (no weapon will be equipped by default) causes the female pawn to never animate.
However, walking over one of the weapon pickups on the map will suddenly transform her from the A pose to full animation.
Point being this seems like something innate to how the animations are being done in Lyra and/or ShooterGame. I’ve not yet discovered if it’s a bug or a feature.