Yes I know there are tons of threads regarding this issue and it points as to how widespread the problem is with Ford's equipment. Rather than posting same comment on hundreds of threads I will share it here. Feel free to pass along.

The solution is to replace the APIM which is part of the radio/head unit. I had read that this was the only thing that would resolve the issue and worked with my local Ford dealership to get the old system updated/reflashed/refreshed to document the issue would not resolve. Then they ordered the new APIM. Took about half an hour to install the new one. Mic problems are gone.
Absolutely makes sense now that I think about it. In my 18 250 I didn't have any issues like this. On top of the mic issue I also randomly experienced the gps getting lost, compass reading off, bluetooth echoes of my voice to people I was talking with, back up camera not coming on all the time, etc. None were persistent just random and all controlled by same APIM.
Just wanted to share. I know some folks came at me and said it wouldn't work because they were all bad in all their trucks ( I believe that too), the problem was with Apple (it isn't and never was)(we have 3 vehicles all with CarPlay and three iPhones; problem stays with the truck across all 3 phones), etc.
So there it is. Replace the APIM and you can use CarPlay as intended without people saying they can't hear you on the other end.
Of course you can just as easily get a new APIM that is faulty which is why I have spent the last week and a half testing to make sure the problem didn't reoccur. It has not.
So to sum if you are experiencing mic issues with CarPlay and the caller on the other end of the call can't hear you or reports they can barely hear you then replacing the APIM with a non faulty one will immediately resolve the issue.

 

I have not had any issues but will keep this in mind if I do. Thank you for posting.