I don’t think this is actually a myth. I think there’s an extreme version of the statement, but it nevertheless is true that there are specialized taste buds and that they aggregate on sections on the tongue.

And I think there’s a whole rabbit hole here, of overeager “corrections”, that are not in fact corrections but just someone engaging in bad faith with a statement that’s close enough to the actual truth. It’s actually more wrong to categorically dismiss it, then it would be to note the difference between it and the truth, which is to say while they are not strictly regions, they’re nevertheless as attested to be the NIH:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8956797/

There is undoubtedly a spatial component to our experience of gustatory stimulus qualities such as sweet, bitter, salty, sour, and umami, however its importance is currently unknown. Taste thresholds have been shown to differ at different locations within the oral cavity where gustatory receptors are found. However, the relationship between the stimulation of particular taste receptors and the subjective spatially-localized experience of taste qualities is uncertain. Although the existence of the so-called ‘tongue map’ has long been discredited, the psychophysical evidence clearly demonstrates significant (albeit small) differences in taste sensitivity across the tongue, soft palate, and pharynx (all sites where taste buds have been documented).

In my opinion, the more interesting phenomenon is understanding how these facts, and the temptation to correct, challenges our ability to sustain nuance and to carefully differentiate between degrees of truth, instead of just making blanket denials.