Yes. Thankfully, the point is that using the regular container model you don't need memory page sharing, because there's only one kernel anyway, not a copy per each container.
And they share a CPU, too. Please come back with an actual point (like a link describing a attack on encryption using that shared cache), as I don't have time to make one for you.
Administrators may revert to the previous behavior if they so wish.
Sounds like a sane change to the defaults, but anyone who isn't securing against 3rd party code can turn it back on (to return to much more Docker-like security/performance).