I see where you are coming from on this.
Yes a 'something to drink?' works for a general drinks run and it's only in my experience that they ask if you want wine only with the full meal service. And that applies to many airlines not just BA
On my LGW-AMS flights they ask if I want something to drink so leave it open as to what to ask for.
But I can see some people thinking if they didn't offer wine especially with the meal that the CC thought they had already had too much to drink of that it had been 'enhanced'!
And whilst I guess it could be added to the i-pad such a note would only be effective if (a) it got read by the CSD/M and (b) if they did that they then told the rest of the cabin crew.
And that's before you start to look at what else is on there that could be seen as more important than a personal preference (of course it's an important preference for you) such as an allergy or special meal which could have other implications.