theverge[.]com/2019/3/27/18283674/microsoft-april-fools-day-ban-pranks-internal-memo
Love it or hate it, April Fools' Day has been around more than 100 years, with variations in several countries, so some of us do enjoy it. Done right it's useful for marketing, e.g. ThinkGeek[.]com, where it builds traffic & even has led to new product offerings. Done wrong people get upset, so most companies just ignore it -- an outright ban is, to say the least, unusual, especially when that company has traditionally participated.
Unfortunately the author of the linked article takes a somewhat negative view of April Fools' Day, and so ignores the all too possible, and very sensible reason for Microsoft making this unexpected move... the public release of Windows 10 1903 is very imminent.
You can easily imagine the following...
"Windows 10 1903 is available for seekers and will start being rolled out April 9th through Windows Update."
"No -- Seriously -- We Really Mean It!"
"C'mon guys, what's the big deal?"
"No! We're NOT joking!"
"Yes! We Actually DID Test it, and it's working."
"Well no... I didn't install it on my mom's laptop yet, but I will I suppose, eventually... but that doesn't mean it's not ready!"