DD is interested in Biological Sciences, so I did a quick look at a uni comparison website to see where courses were offered. Was interesting to see that Oxford offers a BA as opposed to what (I would have expected) BSc. Which got me wondering - what make a course a BA or BSc? In my ignorance, I assumed BsC was 'science', and BA 'not science'
First degrees at Oxford (and I think Cambridge) are traditionally BA. For example DH studied physics there and has an MA (Oxon) - and the MA is (or perhaps was) given to graduates after about 5 years if they coughed up £20 ... though this may have changed since the dark days of the last century!
I think with a lot of things there is 'normal' and there is 'Oxbridge' - they like their traditions, and if that means they are doing things differently from everywhere else, then they don't see that as a problem.
In general, Biological Sciences and similar subjects will be a BSc, because it stands for Bachelor of Science. Whereas BA is Bachelor of Arts, so as you say is 'not science'. You also get more specific ones like BEng or BMus.
It really doesn't matter - some universities (like Oxford) only give one type of degree. I have an MA in physics (as a first degree) from Oxford too. Others do a science/arts split. Others have a wide variety, almost one per subject. Some may think that a particular subject is an arts subject and others may call it a science subject.
Provided there's a B at the start (or an M, for Oxford / some 4 year courses) and "honours" mentioned somewhere, they're all equivalent undergraduate degrees. I mean, some are more respected than others, but you're not going to discover that actually it's not considered to be a degree, which you might if it's called a diploma.