So we have these matter particles that are defined by three numbers, a weak hypercharge Y in the set {1, 1/3, -1/3, -1}, a weak isospin T in the set {1/2, -1/2}, and a ‘generation’ in the set {0, 1, 2}. The electric charge is a derived quantity Q = T + Y/2 that does not depend on generation. For generation 0 we have the particles,

T Y Q name
-----|-----|-----|----------
-1/2 -1 -1 electron
-1/2 -1/3 -2/3 antiüp quark
-1/2 1/3 -1/3 down quark
-1/2 1 0 antineutrino
1/2 -1 0 neutrino
1/2 -1/3 1/3 antidown quark
1/2 1/3 2/3 up quark
1/2 1 1 positron

The weak interaction has to preserve these quantum numbers, so for example when a free neutron (up-down-down) turns into a proton (up-up-down) and an electron, as it will do if you leave it alone for about 15 minutes, then one of the down quarks is turning into an up quark and an electron. This preserves electric charge but it does not preserve the underlying quantum numbers, so it requires emitting an antineutrino. [The fact that you need 4 particles total is part of why it takes a long time on the order of minutes; in this case the Feynman diagram vertexes only have three lines going in/out and so creating a 4-particle state requires two of them, in the middle you have a W- boson, (T=-1, Y=0).]

And then there are some things which are not present but fit the quantum numbers, for example many grand unified theories predict something which is spectacularly unobserved called “proton decay” where an up (1/2, 1/3) could hypothetically annihilate with a down (-1/2, 1/3) to generate an antiüp (-1/2, -1/3) plus a positron (1/2, 1)—this would manifest as a proton decaying into a neutral pion (up-antiüp) plus a positron, which would presumably be hugely energetically favored (protons have several times the mass of pions and elecron/positron masses are negligible)... this sort of decay does not have a way to happen in the standard model because there is no interim (0, 2/3) particle to sit between the two vertices.

Anyway, the next generations up are basically copies of the same 8 matter particles, with "electron" replaced by "muon" and then "tau", "neutrino" replaced by "mu neutrino" and then "tau neutrino," "down" replaced by "strange" and then "bottom", and "up" replaced by "charm" and then "top". The down and up quarks typically cannot decay into anything without some antidown or antiüp quarks sitting around to annihilate with them, though again, this is not 100% obvious from the table above, as the case of proton decay shows. So that we have observed this with strange and bottom quarks is two out of our four possibilities.

So what this makes very clear is that the CP-violations are not something specific to the (-1/2, 1/3) / (1/2, -1/3) antiparticle pairs that are called (anti-)down, (anti-)strange, (anti-)bottom in the three generations. It is not some sort of physics phenomenon that requires these two signs to be opposite; it has now been observed in the (-1/2, -1/3) / (1/2, 1/3) antiparticle pairs, too. Assuming that the presence in the bottom quark means that this asymmetry crosses generation lines, then we are all but assured that the much harder to measure top quarks would also display the asymmetry, and it is something very fundamental, rather than some as-yet-unappreciated aspect of the coupling of isospin to hypercharge.