If Manual flight mode is selected, only traditional PWM with discrete refresh rate will arm the ESC.
PWMSync - does not output any signal.
OneShot125 & 42, MultiShot and DShot - they produce output, but with 50hz refresh rate, which is apparently not often enough to arm modern ESC running BLHeli_S.
It is reasonable to assume that without stabilization task driving actuators (manual mode), there must be otherwise fixed refresh rate for outputs, no matter which ESC protocol is running. The real issues here are:
PWMSync giving no output at all.
No control over refresh rate in manual flight mode for *Shot protocols.