Instruction prefetch read hits the variable address. Either it happens when branch is executed (branch + next word/long gets loaded depending on alignment) or when jumping to RTS and RTS address is not long aligned (prefetch would load low word of variable and opcode of RTS)
It can't know if it is self-modifying code or just a harmless side-effect.
Keep variables further away from code. (I personally prefer using A4 or A5 as a base pointer to variables, I hate unnecessary absolute addresses
)
There is no option to disable kit, at least not yet.