Similar to P30DebugMode, enabling/disabling this option will enable/disable several other features. Here's the proof:

                LCB    A, 0547eh               ; 53A7 0 02 08 909D7E54
                STB    A, r0                   ; 53AB 0 02 08 88
                MOV    DP, #003d3h             ; 53AC 0 02 08 62D303
                LB     A, [[[DP]]]                 ; 53AF 0 02 08 F2
                STB    A, r2                   ; 53B0 0 02 08 8A
                CMPB   r0, #000h               ; 53B1 0 02 08 20C000
                JEQ    label_53ba              ; 53B4 0 02 08 C904
                LCB    A, 0547fh               ; 53B6 0 02 08 909D7F54
                                               ; 53BA from 53B4 (DD0,P02,B08)
label_53ba:     SLLB   A                       ; 53BA 0 02 08 53
                MB     off(00216h).3, C        ; 53BB 0 02 08 C4163B
                LCB    A, 05475h               ; 53BE 0 02 08 909D7554
                SLLB   A                       ; 53C2 0 02 08 53
                MB     off(002eeh).3, C        ; 53C3 0 02 08 C4EE3B
                CMPB   r0, #000h               ; 53C6 0 02 08 20C000
                JEQ    label_53d2              ; 53C9 0 02 08 C907
                LCB    A, 05480h               ; 53CB 0 02 08 909D8054
                SLLB   A                       ; 53CF 0 02 08 53
                SJ     label_53dc              ; 53D0 0 02 08 CB0A

The value loaded and stored register 0 (r0) in 53A7-53AB determines wether other settings will be loaded. Addresses around 0547xh in the rom contain single byte switches like VTEC VSS check, VTEC enable/disable, etc... some of which are superceded by the value at 0547eh.