Yes, good point. But as PanGalactic says above (and in response to where2travel) it is offered as a statement credit rather than a refund.

I don't particularly expect to get anywhere, but I will be interested to find out the reasoning - and I have also asked whether the spend counts towards the November spend £x get xx MR bonus campaign, or whether because it seems to be treated as a refund that it doesn't count.

I strongly suspect the latter - and at the end of the day I would rather have the money than the MR - but I had the time to ask so I decided I might as well.