First off, per the services agreement, Amazon needs to preannounce policy changes, and did not in this case (or many others). Also, apologies if the search function in the fora is so poor that this is effectively a duplicate of another thread ... the most germane thing I can find is a month ago, when a Mod reiterated old policy shortly before Amazon instituted a new one.
As of today (7/25), OTDR has a new definition, and this at-one-time info-only metric can now kill your account. In this change, Amazon is announcing that they recognize that sometimes stuff -- like hurricanes, riots, state-wide power outages, strikes, etc. -- can happen which will make even Amazon's automated estimate (over which we have no control) of delivery time wrong. When this happens, buyers will be notified, but according to the OTDR page, sellers will not be cut slack. "An OTDR below 90% may result in account deactivation" ... and this metric ("On-time delivery rate without promise extensions") is prior to any extensions. Effectively: if there's a natural disaster in your shipping lane, expect to have your account shuttered. Who comes up with this? Either the description of an unannounced, new-release feature is so poorly written as to be wrong in a way that will make long-time sellers think they'll lose their accounts (ooops! our bad!), or it's accurate and the idea is insane.
Other platforms I can name simply ignore metrics for orders affected by these unavoidable issues. [I bet this doesn't apply to FBA, which is just another anti-trust-worthy measure instituted by Amazon to illegally push people to that platform.]
(p.s. this forum software is also heinous ... making me reload to post, or logging me out mid-screed, and throwing away my work in the process simply doesn't happen in any other forum software I've ever used)