Bombs have never worked on large planets properly apparently. It wasn't actually my breaking, though I actually fixed a bug, let me explain...
In 1.2x bombs were super high damage, so you never noticed it. If you want to test this, decrease the bomb damage to about 1000.
If you bomb a regular planet, you hit for 'regular' hitting damage PLUS prox damage. You are NOT supposed to hit 'regular damage' with proxy damage, that is basicly DOUBLE DAMAGE. This only occurs on planets. However, on LARGE PLANETS SUCH AS VENUS, you will only do REGULAR damage because the prox damage does NOT reach. This happens in all verisons of SF 1.2 to current.
However, I saw the double damage bug and I did adjust it. I had intentions of upping bomb damage to solve the loss of damage as well. But its overall jut good 'coding' rather then leaving it as it was. I never NOTICED however it never did damage to the colony after the 'double damage fix' because a proxy weapon is supposed to do proxy damage only, which it 'doesn't reach' on large planets.
Planets and bound colonies have to be seen as one 'entity', which is the fail reason since 1.2x. I simply fixed the double damage bug, but in turn, since lage planets NEVER HAD PROX DAMAGE on them, you don't see them getting damaged. A rather annoying bug actually but I believe it can be solved with little effort, hopefully.
I'm just letting you guys know what is up with that

You can test on 1.2x if you want to see the 'double damage' bug with large planets vs smaller planets.
The reason why VENUS and EARTH never lost SUPPY POINTS was because of this bug too, although I fixed the suppy damage points because I made planets and colonies one entity when checking bomb supply point damage. It was never because 'earth was a home planet' or other things like that. Although I'm not sure if there cappable even still, venus too never lost supply in 1.2 I believe.
If anything, the fix just let us know of another bug that needs zapping.