I just plugged in my iOS 11 iPhone 7 Plus and loaded up Image Capture. I dragged a 4K video recorded by the iPhone out of Image Capture directly to the desktop on Sierra, and it kept the HEVC format. The file is a 20 second 60 MB 2160p HEVC file with a .MOV suffix. As mentioned by others, .MOV does not tell us what file type it is, as .MOV is just a container. It could be just about anything inside. However, I know it is HEVC because the codec listed is hvc1 under the info (COMMAND-I).
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As mentioned, in Sierra (and El Capitan), the file will not play in QuickTime. However, it plays fine in IINA. If your files play fine in QuickTime in El Capitan, then you don't have HEVC files. You are probably still set to record h.264 files.