Why does the Video format that my iPhone defaults to NOT supported by my Mac software

Because if your MacBook Pro is actually running 10.10 it is 6 major versions behind. When Yosemite was released 7 years ago HEIF/HEVC format didn’t exist. You can either update your MBP or change the camera settings on the phone from Most Efficient to Most Compatible.

What is the issue that you are having? What is the format of the video after you record using camera?