Not true - the family ruined Boddies, 5-10 years before Whitbread bought them. Ron Pattinson did some digging into what happened back in March - it seems to have been a mix of things in the late 702 amd early 80s, including changing adjuncts as some went out of production, changing from traditional barley varieties, using older hops, and perhaps a conscious decision to make it less bitter to appeal to a wider market.
https://barclayperkins.blogspot.com...0-08:00&max-results=20&start=39&by-date=false
And going back to the OP - high-gravity brewing is fairly common in the commercial world, but the kind of 2x dilution used for stuff like Carling is rather looked down, the odd litre here or there is rather different. But yes, things do end up tasting different when brewed up at 8% or so and then diluted down to 4%.