FWIW the hull and turret side armor of the tank which received the blast are 8 and 15cm respectively. The penetration value of the satchel charge is 18cm. So apparently the game at least sometimes assumes close proximity of the target, as if it's in the firing unit's hex, just as it assumes the ability of engineers to clear mines in an adjacent hex. (IIRC a tank got blown up under similar circumstances during an earlier go at this scenario.)
@Aeraaa: Wasn't aware engineers never suffer ill effects of their own ordnance. In that case SPMBT doesn't "mirror reality" with absolute fidelity. But of course perfection is not of this world, n'est-ce pas
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