If people's work from home days aren't coordinated it can save a lot of per worker real estate because you can go to floating desks so you only need to accommodate peak attendance instead of having a single desk for every person. The schedule can be adapted to team needs too so that people working together are in the office on the same days so they can take advantage of in person collaboration when needed.

That is the preferred way for me definitely. And it seems that for quite a lot of people.

I like my coworkers to be people I know in real life; I also like to code in a silent room. One way of accomplishing that would be a private office at work, but hybrid WFH is the next best thing.

You can have a full office everyday if half of the company WFH part of the week and the other half the other part.

At the cost of drastically lowered productivity per person due to hot desking, and not having the space for an all hands.

Do you mean an 'all hands on deck' emergency or an all hands meeting? If the latter that's a problem with an event space not of desk space. If it's the former you rarely actually need everyone present and it's unlikely every department will be needed at once unless the whole company is failing and even then people can work remotely for those too.