An AI chat bot made this sentence: "His caustic remarks left a bitter taste in everyone's mouths during the meeting."

I thought that "mouths" was wrong because "everyone" means each individual and they have only one mouth of their own.
I asked it about it and it answered as below. Is this reliable information?

Both sentences are grammatically correct, but they convey slightly different meanings.

1. "His caustic remarks left a bitter taste in everyone's mouths during the meeting."
This sentence suggests that the caustic remarks affected multiple people, leaving a bitter taste in each person's mouth. It emphasizes that the impact was widespread and affected the group as a whole.

2. "His caustic remarks left a bitter taste in everyone's mouth during the meeting."
This sentence implies that the caustic remarks affected everyone collectively, leaving a bitter taste in the collective "mouth" of the group. It suggests a shared experience and emphasizes the overall effect on the group.

Both versions are acceptable, and the choice depends on the specific nuance and emphasis the speaker/writer wants to convey.

Question

An AI chat bot made this sentence: "His caustic remarks left a bitter taste in everyone's mouths during the meeting."

I thought that "mouths" was wrong because "everyone" means each individual and they have only one mouth of their own. 
I asked it about it and it answered as below. Is this reliable information?

Both sentences are grammatically correct, but they convey slightly different meanings.

1. "His caustic remarks left a bitter taste in everyone's mouths during the meeting."
   This sentence suggests that the caustic remarks affected multiple people, leaving a bitter taste in each person's mouth. It emphasizes that the impact was widespread and affected the group as a whole.

2. "His caustic remarks left a bitter taste in everyone's mouth during the meeting."
   This sentence implies that the caustic remarks affected everyone collectively, leaving a bitter taste in the collective "mouth" of the group. It suggests a shared experience and emphasizes the overall effect on the group.

Both versions are acceptable, and the choice depends on the specific nuance and emphasis the speaker/writer wants to convey.

Answer

I agree with you that ‘mouths’ [plural] is wrong, because the expression is normally used in the singular :  ‘everyone’s mouth’.
It gives us an insight into the way AI works, as we see it has adopted standard formulas to justify its explanation, although closer inspection reveals that, in effect, the two are identical.  There is no difference in nuance or emphasis :  the shared experience and its overall effect is the sum of the effects on the individuals concerned.
The reason the first [plural] version is not used is down to the conventions of use, and has nothing to do with “the specific nuance and emphasis the speaker/writer wants to convey”.  We will have to learn to treat AI with caution.