Real life. CBU distribute warheads every few metres or so, and that is deadly for soft stuff as it spreads the splinter pattern around instead of having them radiate from a single unitary warhead.
However AT bomblets still need direct top hits, and any effect from misses of the tanks is far less than with unitary warheads, of course!. Bombs need such, or to be very large and very close. Unitary bombs can still blow off tracks and running gear or do other disabling damage. Itty-bitty bomblets that miss are of no splinter consequence to AFV, other than scratched paintwork. The spread of bomblets over the target area probably makes the effectiveness go from 1-3% to 5-6% . Which is about double or triple the HE effect, still very nice to have. But AT bomblets are
not an anti-armour "shotgun". In fact, they are not as effective an anti-armour weapon as one might think, and also produce a dud rate of about 5% of the bomblets, ie about 5-6 per typical CBU
linky.
(I may well be adding a few random mined hexes to cluster munitions.. )
Basically, a cluster bomb is like shooting at a flock of ducks with a shotgun rather than a rifle. You
might get another duck than the one you aimed at, but not as often as you would think. Additionally - in real life, the dispersion pattern from air dispensers and CBU is rather linear, (not modelled in the game) - making them better at close-packed road column attack, than on tactically deployed AFV.
Cheers
Andy