> For most of the channel's history they did very little of it visibly. The architecture was permissive of intervention; they simply chose not to intervene much. That restraint is what ended.

I guess it wasn't always visible, but they were intervening in some for or another since the beginning. At WhatsApp, push delay/suppression/coalescing was something we were always monitoring, and IIRC, it was part of the system since at least when I joined in 2011. If you don't work within the system, your users' messages don't get delivered timely.