Yes, the police power has its limits. But what are those limits in a situation like this?
In fact, states may have been able to order their citizens to completely stay indoors, but simply chose not to. We don’t really know. This situation is unprecedented, which means there is not a single case directly on point.
A total stay-at-home order would have been tough to enforce, anyway, and would have resulted in much bigger and earlier political pushback. No one here is in favor of a China-style lockdown — which would have meant something like one person in the home gets to venture out every three days solely for the purpose of getting food. That would never fly here. Americans love their freedom too much.
Yes, now some governors are announcing they will re-open their states within the next few weeks. Will they, in the end? We’ll see. Remember Trump said he wanted America open for business by Easter, then backed off that (not that he has the constitutional ability to make that call anyway).
In most cases, it appears governors will be going against the will of their citizens, which means a lot of people may stay home anyway as you suggest.
Whatever state governors have to say about this, cities, businesses, and individuals will still get to decide what to do.
If it’s true that states can’t force people to stay home, as you say, then states certainly can’t force people to get out and about, either.