iPhone 7 Plus, 256GB, Matte Black here. Same issue. Told my friend who had a gold one to check his and his was perfectly fine. Thought I was going mad at first!
Googled and found this thread which made me feel much better about my situation. Went to the Apple Store to pick up some Beats yesterday so I mentioned it to the people at the Genius Bar, besides the guy on the door telling me it was the Taptic feedback clicking (seriously?!), I spoke to someone else who could hear it clicking! Hurray! Not going mad after all!
I mentioned what you guys had said about screws being loose so he took my phone into the back and returned several minutes later, told me the screws were particularly loose and to check my phone now. Instead of it clicking every time, it does it maybe 1 in 4 "twists" now, but not completely solved.
He was great with me (even though I was the first to have been back to my store with this issue) and told me he would set up a repair and as soon as they get my phone back in stock, I could get a free replacement. Hopefully as they're all out at the minute, I might get a different batch to my current one and the new one won't have this issue.