Except that the M7's front looked like the iPhone 5's back. Also the iPhone 6 looks more like the iPod Touch, which predates the M7.
Lets take a look at the similarities between the M7, iPhone 6, and A9.
HTC M7 and iPhone 6 similarities:
1. Antenna lines (antenna embedded in metal first introduced by iPhone 4)
2. Unibody design (could say the first gen iPhone or iPhone 5)
HTC A9 and iPhone 6 similarities:
1. Antenna lines
2. Unibody design
3. Protruding camera lens
4. Camera lens above antenna lines
5. Split two tone round flash
6. Same shade of gray and gold color
7. Curved glass screen edge
8. Same corner curve radius
9. Same edge curve radius
10. Same speaker, headphone jack, and charging port design
Things removed from HTC A9 that changes its HTC One design language:
1. Curved back
2. Hard edge
3. Chamfered edge
4. Non protruding massive camera lens
5. Front facing speakers
Looking above, it's clear that it's overwhelmingly weighted towards the HTC One A9 copying the iPhone 6 design language versus the iPhone 6 copying the M7. Anyone that believes in the latter needs to get their eyes examined.