Tested Box Selection with Backface Culling on and find inconsistency.
- Box Selection in Object Mode with Backface Culling on, does not select backfaced objects,
in Edit Mode does.
- Lasso and Circle Selection work fine and select objects in any mode.
- If I set active object backfaced to the view, and then Box Select, it select that backfaced object too…
Tested in 2.83.4, 2.90.0, 2.91.0 all the same: