At the time, I have to say I thought this was a rather odd decision. I wrote back in 2016 about how I felt, for a number of reasons, that CAMRA was wrong to draw an equivalence between bottle- and cask-conditioned beers. At least for everyday quaffing beers, bottle-conditioning in practice adds very little while introducing an extra element of complexity in storage and serving and something of a lottery of how it will turn out, as Seeing the Lizards, who has worked in the retail trade, pointed out:
Although the purists may not like it, it’s a fact of life that most buyers of Premium Bottled Ales tend to avoid ones that are bottle-conditioned, so it is a sensible business decision from Marston’s. Few consumers are going to do something out of principle if it gives them no discernible benefit.
The perception of BC PBAs, is that one third will be flat, one third will be as intended and one third will be gushers.— Seeing The Lizards (@seethelizards) June 18, 2023
Over the years, a number of other brewers have taken the same course including, for example, Hop Back Summer Lightning. Most bottle-conditioned beers now seem to have disappeared from the major supermarkets, including Fuller’s 1845 and Bengal Lancer, Worthington White Shield and Young’s Special London Ale, and the only ones I still see regularly are Shepherd Neame 1698 and St Austell Proper Job.
As I said in the conclusion to my post,
Yes, at the end of the day, bottle-conditioning, if done well, does add something to a beer. Bottle-conditioned beers can be regarded as the crème de la crème. But, because of the practical difficulties involved, and the fact that the process adds very little to lower-strength quaffing beers, it is best reserved for higher-strength specialities.