This is pretty standard for a takeover process. As the sale is far from complete it’s normally considered safer not to make any changes that could threaten the sale or commit the company to something the new owner doesn’t want.
I have only personally been through one acquisition personally but I do follow the game industry acquisitions. In those cases the companies have continued to largely operate as if nothing is happening until it actually closes.
If for some reason the deal doesn't close it is a huge risk to the company to not continue to operate as normal.
There's also the underlying idea that perhaps Elon has said he has big plans, but no one at Twitter knows what those are and if they even exist. Better err on caution with Fickle Musk.
Their major problems in many fronts have remained unsolved for a long time (e.g. spam bots, readability of long threads, functional bulk block lists etc.).
They aren't even that good at the one thing they seem to be passionate about: censorship.
Twitter on the other hand has such an extreme political bias that bias is written right in to the (current) rules for the platform
To compare the 2 is laughable
"Twitter Inc. locked down changes to its social networking platform through Friday."
No major changes in product direction, yes, obviously. You don't want to kill the goose that laid the golden egg. No changes at all - and only for a week - is pretty clearly a sign that Twitter management fear emotional kneejerk extremism in their own employee base. The fact that they have to do this speaks volumes about the problems inside the company.