Unexpected limitations on "Updates" folder? Apple sent me 4GB of updates to go to macos 10.14.5 this morning. As I have several systems needing this update, I thought I would try to save the contents of the /Library/Updates folder to use rather than allow each system to DL the 4GB of data. I was able to copy the contents to my desktop, but when trying to delete the update from /Library/Updates so that I could replace them with my copies to test my theory, I found that the system would not allow be to do so. I couldn't delete, move, or chmod the parent directory, or any of its contents. Command line returns "Operation not permitted". Whoami returns "root", but apparently not. What's up with that, any ideas?
On one system, before you install the update - enable caching in the sharing preference pane. Save the cache files to an external drive - speed there isn’t much of a limiting factor since the downloads stream well and any recent hard drive or SSD will be almost as fast as the network can serve files.

Then the first machine to do the download will get the file cached. All the rest of the machines will pull from the cached version.

This is much better than trying to stage the updates on each system as the permissions and code checks are designed to not let you easily place a file on macOS for updating.