I have read a lot of BS regarding that topic recently (for instance-> here, which strangely do not respond to comments) . Trying to “review” such and such product, but clearly biased toward one and not giving much favour to the other. This led me to revive a video I made a couple of months ago but never ended posting because the sound was so bad.
So I did a new voice-over and here it is.
This test shows 2 users on the same document, in a Google doc and then in a Word online document. It came up as I was training a group of end-user in Office 365 and demonstrating having 6 people collaborating, one of the users was so relieved to see the experience they were getting. But no spoiler, check out the video to see what happens.