1) Except that the entire premise behind BitLocker TPM's security relies on the login screen as a hard security boundary, and thus any attack on the login screen is an attack on BitLocker. It is semantics to dispute this and certainly fits "downplaying."
2) I'm sure many organizations are thankful that the researcher has decided not to release that exploit chain at this time. I am hopeful that Microsoft will not be as dismissive and will resolve it before it is publicly released.
3) It distracts from the point. The point is that Microsoft's security record is so bad that many of the vulnerabilities appear deliberate and obvious enough to be backdoors.
4) Yes, this also fits the definition of downplaying.
1) It is semantics to dispute this and certainly fits "downplaying."
It's not semantics. A true bitlocker backdoor would let you in even if it's passworded.
And is it really downplaying? The ability to shove in a USB stick and get control over the drive is mostly equivalent to a bitlocker exploit when it comes to laptop theft. But for quick access to a desktop without bitlocker, and without the ability to open it and pull the drive, it's actually more damaging than a bitlocker exploit.
2) I am not personally being dismissive of the claim. I'm saying it's fine to hold off, and even if we assume the PIN version is real we shouldn't assume we know exactly what it looks like.
3) Saying it's not a backdoor distracts from the point? Can't agree with you there at all. The comments saying it's definitely a backdoor are the ones I point to as distracted.
4) Maybe it's downplaying but it's true. Replying on TPM-based bitlocker is a lot more dangerous than having a secure password. It's chosen because it's easier to enforce.