Well let's unbury the new guy's thread and give him an answer shall we??? (Sorry for delays)
The B760 Morter Max is the only MSI B series board I am aware of with an external clock generator that will overclock the reference clock or bus clock of the CPU. Only certain B600 series boards have the external clock generator also.
13th and 14th Gen Bioses are patched to prevent overclocking bus frequency. And obviously Z series boards are required to overclock via the cpu multiplier.
TLDR - No. There is no way to enable this.