Uh, no. He's said multiple times now that the individual bombs are a lot weaker than firebombs. If the numbers don't add up properly, then that's something which would be fixed in balance testing / patches. Assuming this system was implemented.
It's an interesting idea, but I have to wonder how much work it would take just to even TRY it given it would probably require massive code rewrites for ASFs, and that's a lot of manpower and resources spent on a gamble.
HE: Does 500points Kinetic and 400missile damage (roughly 2/3rd old FBomb values). Splash of 20m. Fairly inexpensive.
So with the Sulla's 9 available bombs, times 0.6666666666666666667, gives you 6.000000003 F bombs worth of damage, along with your existing weapons. Oh yeah all this with no additional weight. I still think its a flawed design, unless your bombs equated to the damage equivalent of an AC20 or something more reallistic.
Yeah your numbers are right, strictly speaking they should have an IS PPCs worth of damage (474/474) but there's 2 things that I already said that made me suggest the slightly higher numbers:
1) That Sulla would be at massively reduced maneuverability and speed, easy pickings for AA, stream-lined ASF (no bombs) and random groundfire alike; there should be a reward for the payoff and 1 IS PPCs damage seems pretty poor reward, but again it would have to be tested.
2) The Balancing concept of Bomb Doors: In my example would limit that Sulla, as a medium ASF to a maximum of 3 Bomb Doors (meaning ~6s reload x3 to drop all 9 bombs), that's 2 current FBombs worth of firepower for each bombload (but all 3 need direct hist instead of 2, placement of bomb-doors, ie. where the bombs spawn can effect this also I assume).
The main change is that Bombers are now no-longer a separate variant that strips weapons to be as maneuverable as the Primes, they are the Primes etc. with bombs loaded, and incremental penalties for carrying them, sure ASF pilots that are planning AA work will never load them, some folks will load up just the minimum to stay almost as maneuverable and drop them either when they see an enemy ASF or when they finish a strafing run with the primary weapons.
Strafing is something we should encourage. Bombers would also be easier for AA to hit under an Aerotech based system, and this should be encouraged too.
EDIT: And BTW an AC20 is something like 800/800 damage, so that'd be insane buff to the bombs from what I suggested

EDIT: IS PPC damage correction.