In general, I think of how TA (titratable, or total acidity) and pH impact flavor and mouthfeel in this simple (and yes, perhaps simplistic) way: TA determines how tart or sour a wine tastes while pH points to how a wine feels in the mouth. TA and pH typically won’t change in the bottle over time, unless you had a lot of residual sugar or residual malic acid and then had a refermentation in the bottle. If the wine is unfiltered it’s technically possible that spoilage microbes could engage in enough metabolic activity where they might be consuming acids or sugars and excreting by-products. A great example of this would be if there was residual malic acid in a wine and then malolactic bacteria had a feral fermentation in the bottle. This would certainly raise the pH of the wine, as lactic acid is roughly half as “acidic” as malic acid.
It’s hard to say whether consumers really benefit from having a wine’s pH and TA listed on the back of wine labels (or on wine lists). I would wager that most consumers have A) no idea what TA and pH really mean, as they pertain to wine especially, and B) no basis for comparison from which to draw conclusions even if they were given those numbers. It’s not that I have a dim view of wine consumers, it’s just that I think consumers care more about the overall taste profile (I call it the ‘yum factor’) of wines rather than technical details like wine chemistry parameters. Any general-market wine that’s going to “fit” in a consumer category or on a wine shop shelf (which means it had to be vetted by a retail buyer) is most likely going to be within acceptable parameters anyway. Therefore pH and TA might be useful to detect a winemaking fluke (say, a Sauvignon Blanc at a pH of 3.80), but then winemakers who know what they’re doing would probably never put those wines in the bottle anyway.
Even as a winemaker with many brands and products under my belt, I only ever use TA and pH (and most wine chemistry parameters, for that matter) as distant guideposts. As long as I know that my wines are in a “safe” range of wine chemistry (pH’s 3.70 and under for reds, 3.60 and under for whites) I really don’t care whether the pH is 3.57 or 3.49. I make my moves by taste and balance from the vineyard to bottling, only making tweaks along the way as necessary. Each wine is its own unique complex chemistry soup and so trying to compare pH’s and TA’s, and to use them as a basis of wine judgement is really comparing apples to oranges. I go by traditional sensory analysis much more than chemical analysis and I think the trade and consumers are much better served if they can taste a wine instead of, or in addition to, reading numbers on a label. Am I happy to provide the TA and pH of any of my wine projects to anyone who asks? Sure, knowing more is not a bad thing per se. Though with every vintage and every wine its own unique animal, I’m not sure if these small differences are meaningful.