The unibody build of the M9 makes it a though nut to crack. iFixIt has bravely dove underneath the M9 undeterred by the unfriendly design of the M8.
HTC just isn’t in favor of making easy to repair devices it seems. It is a good thing they introduced the Uh Oh protection program where they will fix physical damage for you.
The jest of the teardown guide is that the teardown starts off easy, but gets hard. Fast.
The motherboard seems to be glued down to to battery making both extremely difficult to remove without damaging one.
It also appears that the rotary vibrator is actually soldered down on top of the motherboard with some added adhesive for good measure.
There is no mistake, the HTC One M9 is solid device built with quality in mind. It is just a little hard to fix if said quality were to be hindered by human clumsiness.
You can read the whole teardown walk through with all of iFixIt’s quirky jokes.
Do yourself a favor and take good care of your M9; maybe even put a case on it. If your M9 takes a little damage, it might be best to send it in to HTC and let them fix it up for you.