2023 M2 MacBook Pro battery health drops to 99% after only 36 cycles. Normal?

It's not abnormal.

Maximum battery capacity does not decrease at a linear rate. In fact it may even increase from time to time. It is therefore not a mathematical function, meaning it is not possible to extrapolate its maximum capacity to any future date. The long term trend measured over a period of years is down.

Although it was written primarily for iOS devices, you may wish to review When to charge your iPhone or iPad - Apple Community. As he states, "While this tip is specifically for iOS devices, the same principles apply to all other Apple devices (watches, AirPods, MacBooks) as well as most other manufacturer’s products that have Lithium chemistry batteries."

About battery health management in Mac notebooks - Apple Support

Manage your Mac laptop’s battery - Apple Support

My thoughts are that it cannot possibly help, and if a product or app does not provide a tangible benefit then it should not be used.

Apple thinks about these things. If any company, individual, developer, claims Mac power management knowledge superior to the company that spends countless engineering hours devoted to the subject ought to be treated with extreme suspicion, if not outright derision.