PH and sour / acid taste

There's a bit of trickery going on in the comparison of vinegar (acetic acid) to spirits of salt (hydrochloric acid). Your 5% (0.83 molar) vinegar has a pH of about 2.5. You need much less of the stronger acid, HCl, to reach that same pH (2.5); in fact only 0.003 molar, a factor of 277 less. Since you taste the anion (acetate or chloride), not the proton (H+), it's no wonder that the vinegar is much more flavorful; there's a 277 fold difference in the concentration of the flavor agent. Pick a different acid, and you'll get a different tasting anion, and a different concentration needed to reach pH 2.5.

Response to comment on taste of anions:

Your linked Wikipedia article gives the impression that the taste reception system is fairly simple, and well understood. It is neither.

Here are a couple examples of reasonably current research on the taste of anions:

The Anion Paradox in Sodium Taste Reception

Anion size of sodium salts and simple taste reaction times.

Take a look at Wikipedia's article on taste receptors. you'll see that 'bitter' tastes are subclassified by 30 or more different receptors. Salty taste receptors (specific anion and cation) are still are poorly characterized

Research on humans is hard, so it'll probably be decades before the mechanisms of tasting are fully sorted out. Until then, consider sources like Wikipedia expositions of the current state of knowledge, rather than the final word.

Weak acids change pH about half as much as strong acids when diluted. Anything we consume gets diluted by the water in our saliva, which will raise the pH of a strong acid solution such as hydrochloric acid more than it raises the pH of a weak acid solution such as vinegar. Also, our saliva is a buffer solution, and the pH of our saliva is significantly greater than the pka of acetic acid, which means that the vast majority of the acetic acid would be ionized at that pH, making it far more effective at changing the pH of the buffer solution than extremely diluted hydrochloric acid. So even if the vinegar and hydrochloric acid solutions had the same pH, the pH of the vinegar solution mixed with saliva would have been far less than the hydrochloric acid solution mixed with saliva.

We have sensors (buds) on our tongues and noses to detect compounds, these sensors send signals to the brain that are interpreted as taste and smell. I include smell in this answer even though you are asking about taste because smell is a huge component in taste, which is demonstrated every time you get a cold. These sensors detect specific flavors in foods, but not every flavor or odor has a sensor that detects it. Humans have learned what they can taste and what they can't, which is why we cook with vinegar and not spirits of salt. It may be possible that what we detect as sour has nothing to do with acidity at all, but the taste of the compounds that come along with the acids we eat.

I'm not sure exactly what the authors meant by total amount of acid rather than the PH. My guess is that the microbes that make the dough sour produce a wide variety of acids and flavor compounds that stimulate your flavor and odor sensors in a broad way, making the flavor and odor more intense.

The current dominant theory in taste physiology is that sour taste arises from intracellular H+ ion blockage of K+ channels. Thereby causing receptor depolarisation and thus signal transduction proportional to the H+ ion concentration INTRACELLULARLY.

Weak acids have a higher tendency to remain undissociated in the saliva and thus remain non-polarised allowing it to cross the membrane of the receptor cell. Once inside it can release its H+ ions causing the sour taste.

Strong acids would not be able to enter the cell as they would have dissociated extracellularly.