Test the idea manually first
Before automating anything, turn Bluetooth off from Control Center or System Settings, put the Mac to sleep, and compare the next similar sleep session with your usual result. Restore Bluetooth when you need it. Keep a wired or built-in input method available so you are not locked out of your normal workflow.
Test one condition at a time. Do not also replace a dock, change network settings, and change sleep preferences in the same session. A better result after several changes does not identify which one mattered.
What a WattGuard rule can do
WattGuard can use sleep as a condition and Bluetooth off as an automation action while the app is running. Its automation state is restored at the end of the rule. The rule is useful for repeating a deliberate test or routine; it does not prove that Bluetooth was the cause of a wake or guarantee a battery result.
In the Store edition, Bluetooth automation uses user-installed Application Scripts and imported Shortcuts. Full controls Bluetooth directly, subject to macOS access and licence activation. If the Store setup is not appropriate for your Mac, use the manual macOS control instead.
Check the follow-up session
Review the sleep period after one change. WattGuard can place the resulting sleep, wake, and charge-change history together, but a wake reason remains a clue rather than a causal allocation. Compare a few normal sessions and stop the experiment if Bluetooth is required for your input or accessibility setup.
When Bluetooth is unrelated to the symptom, leave it on. A routine that disconnects equipment you rely on is not a general-purpose battery fix.