Yep, most will simply adjust the local water profile to suit. Secondly, each style of beer has a different profile required for best effect, meaning that the water is always treated, no matter what. I also find the story about XXXX interesting as I don't understand why that beer wouldn't have had a profile as part of its standard recipe.
The big breweries use mechanical separators instead of fining agents and temp? It's an honest question, I only know craft processes, I wouldn't have a clue how the commercial swill processes work.
They usually use both separators and fining agents, depending on what they are brewing they may just bleed off the bottom and transfer it but everywhere is slightly different.
RO is pretty common in large scale brewing and soft drinks as it keeps the water consistent
As for recipe details, the malt is usually state sourced, as well as few other factors in the brewing process, can affect the outcome of the beer, so is usually tweaked per site. So what is done at one one site may be done differently at another, to get the same consistency, each must taste the same. Some people can really pick the difference but they are usually where it’s there job to tell the difference hence why they have taste panels daily.
With the XXXX that’s unusual as most places will not let some out the door if it’s not the same profile, that can hurt a brand big time.