Do Moogerfoogers have “true bypass?”

No. In the MF-101 and MF-102, the signal always goes through the preamplifier and drive circuits, so the drive control is always active. 

In the MF-103 and MF-104, the output level control allows the user to balance the levels of the “phased” and bypassed signals. In the bypass mode, the MF-103 and MF-104 pass the signal through one buffer amplifier, but do not pass it through the drive control. Thus, the signal is not amplified or “colored” when the unit is in bypass mode.