No doubt, there is a disconnect between the marketing implications and actual implementation, as is unfortunately all too common in marketing. But your words "severe weather" and examples like you cited of "extreme weather" being used in the first paragraph are the key. Just like so much marketing, the devil is in the details, and Tesla's own site describes the functionality using "severe weather" as the first words (
Storm Watch | Tesla Support). I do wish Tesla would be more transparent in their marketing as they absolutely push the boundaries of being inaccurate. Their website at least indicates that they rely on the NWS as a primary driver of storm watch.
The issue is that not every storm is defined as severe, but outages can still happen. Sometimes it depends on bad luck, and sometimes it may indicate one is an area that had grid issues that make it prone to outages. Tesla cannot handle all of these cases, so users have to be prepared by setting a high reserve or accepting the risks otherwise. However they feel Storm Watch may have been presented to them, that is the reality that needs to be accepted, even if one works to get Tesla to change/improve the system down the road.