That one can be realized client-side (just don’t actually pause the stream download, but rather write it into a buffer). No idea, if there actually is a client that implements this, but it is conceptually possible.
I rather meant that with a livestream, people don’t want to be several minutes behind. They want at most a few seconds delay, so they can collectively chat about the things happening in the stream and reasonably hold conversations with the streamer.
What you can do as well, is to just pause the stream when the ad starts and then reload when you imagine the ad might be over…