What the heck happened here?

https://wiki.bambulab.com/en/software/bambu-studio/reduce-wasting-during-filament-change#wipe-into-infill

NOTE: It is NOT RECOMMENDED to enable this option when an object is printed with a totally opaque filament. Otherwise, the mixed-color infill may be visible outside.

I belive it can be similar with dark and lighter colours also

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