Sentry's Rest. When you take a long rest, you must spend at least six hours in an inactive, motionless state, rather than sleeping. [...]
Warforged Resilience. [...] You don't need to sleep and don't suffer the effects of exhaustion due to lack of rest, [...]
(Wayfinder's Guide to Eberron, emphasis mine)
While Sentry's Rest states the rest must be taken, Warforged Resilience seems to indicate there is no penalty for not doing so.
What are the actual consequences for a Warforged that does not go inactive during a long rest?