In this case Twitch has plentiful resources to speak with the group being addressed, so it is possible for them to determine what's appropriate and they don't need to resort to a "First Rule". I don't think the article makes it clear if they've actually done this.
From the article, Ablegamers COO Spohn whose Twitter thread is in the OT seems to draw some equivalence to "gay" and criticizes using "blind" as an alternative term for a negative experience. I'm not sure the usage of "blind" in this tag is equivocating it with a negative experience. There's a difference between calling someone "blind" as in "stupid/ignorant" or calling an experience or experiment "blind" and referring to a lack of information being present. When I see the tag "blind playthrough" I think of it in the same context as a
"double/blind experiment" where information is concealed.
It is inappropriate to make outbursts like "are you fucking blind/deaf" because they tie those disabilities and experiences to some kind of negative outcome, but in the context of "blind experiment / date / playthrough" I don't think it carries that negative connotation. I have a similar feeling about how the word "master" should be scrubbed from usage when used in a "master / slave" context (such as in some computer science terms) but doesn't have that same problematic connotation when used in "Master Chef" or "Master's Degree" since they imply a mastery of a craft as opposed to being a master of some subservient entity.
At the end of the day, we should defer to the preferences of the group being addressed, this is my attempt to understand it. As others have stated, Twitch could be doing a lot more to address accessibility and stamping out prejudices from their platform, one hopes they're sincere about it.