What’s the difference between “concerning” and “regarding”?

This piece from the grammarist discusses about the usage of "concerning" and its possible overtones as "a cause of concern", but apart from that I think that it is interchangeable with "regarding":

• One complaint against concerning does stand up: The word is also a preposition meaning in reference to or regarding, and the adjectival concerning can cause confusion when readers or listeners initially interpret it as the preposition.

• For instance, if you hear someone say, “His email was concerning,” you might at first expect something to come after concerning. This complaint isn’t a rock-solid case, though, as many words in English have multiple functions, but it’s a good reason for those inclined against the word to continue avoiding it.

Actually checking with Ngram, (a question concerning vs a question regarding) it appears that "concerning" used as a preposition meaning "regarding" is quite common.

Among definitions from Webster’s 3rd International Dictionary, 1967 (paraphrased and compacted):

Concerning - To relate or refer to; To be the business affair of. )The use of concerning as a synonym for anxiety- or distress-provoking or "as a cause for concern' was considered archaic.)

Instead, to describe something as a cause for worry, one might use the word

Disconcerting - 1. To shake the composure of; 2. Causing a loss of composure or self-possession, disturbing.

Example: It is unsettling to hear the term “concerning” used so frequently as a descriptive, when the speaker usually means “disconcerting.”

Therefore, "concerning" and "regarding" could reasonably refer to some affair or business matter, while it is perhaps better not to use "concerning" as an adjective or adverb.