I haven't had a lucid dream for a long time, but used to make this mistake too and wake up.

I love the parent comment's description about the system detecting a "glitch in the matrix".

Though I feel it is just if you rouse your consciousness enough you will just break the sleep state.

I do wonder if lucid dreaming affects how rested you are from sleep.

My intuition is that the mind resting comes during deeper sleep and during REM the mind is kind of freewheeling anyway.