First, I've never seen or heard of such a thing happen to cabbages before.
A photo or two on the cabbages would be helpful (IMHO), so we can see exactly what you are talking about.
Also, I've just returned home from my local feed mill, while there I asked them about your particular situation, below is a summary of what they had to say:
Never seen or heard of such a thing before.
If the cabbages had bolted, you would have seen flowers, then seed heads ie The cabbages would have gone to seed.
Sounds almost like some kind of "mutation" has occurred.
Leave at least one cabbage in the ground to see what happens.
Below is what a few gardening "experts" on twitter have had to say, after asking them to take a look at the question:
@simiansuter - I've found what's described can happen where conditions are not "A1":
Not enough light or water.
Lack of pesticides, chemical fertilizers, etc. The mutation is "normal" when grown organically.
I've always grown organically and have often had "tall" cabbages. Generally they taste just fine, which is the important thing.
@Rhizowen - If they were transplanted before getting into head mode, this could have put them into shock, the result being the "mutation".
- Earthing them up is probably worthwhile, might get adventitious roots developing for enhanced feeding and stability against wind-rock.
@MarkDoc - Mutant veg should be encouraged! If it tastes great, who cares.
@timandjoe - No we've not seen anything like that, but it makes harvesting them a whole lot easier :)