Quick hot take.
This is not the first time SE has banned people publicly for stuff on stream, and they did ban a "former" WOW streamer for being openly toxic, on Discord. But generally the Dev team doesn't watch the Twitch & Youtube streams, they are only aware of what is reported, and they were happy for the increased traffic, but I doubt they have time to watch a twitch stream. The big reason this happened was the Dev team and Yoshi-P were watching the stream for the world first. This was a fairly large public event and lots of important people were watching.
Also there are degrees of bad. The UI fixes, and Speech Bubbles Addons, which violate the TOS harm no one, and frankly SE and the team should consider making those for the current UI as options. Damage Meters which do have positive uses are used as weapons by toxic people when they are allowed, and DBM style addons are counted as cheating esp in a progression raid. So there is a fairly substantial difference in levels of offense.
Honestly there are a couple of long time FFXIV streamers who use the bad Addons, but they are usually smart enough to hide them from their stream, even if they comment of their uses casually in their stream. The same Streamers btw who have done interviews with Yoshi-P, and are well aware of why the TOS says what it does.
Also many of the converted WOW streamers (not the trendy came here ones, but the ones who are here to stay.) Have publicly apologized for using some addons as they were unware of the issue in the community and the always present rage against addons some of us have. (ie former WOW players who have been here a long time, myself included.)
I will always report evidence of ACT or the DBM clone, I won't report Speech Bubbles. As I want the UI to include that option. Same with UI clean up Addons, or people using clothing mods for their own personal enjoyment (ie Viera Hat Mods, Sexy Male bodies, etc.), if you want a perfect screen shot, or RP session, that is all for you, I don't use any Mods or Addons, and I only fight against addons that impact others.