I can confirm this is happening.
I just got a report about this in my community as well. People who thought they were being emailed immediately of all new posts with mailing list mode are now set up to get daily updates.
Here’s what my CEO’s preferences look like right now - he wants to get EVERYTHING in his email IMMEDIATELY as it is happening, but now he is apparently getting daily updates. Did something change recently in the default settings and in the settings of existing users? If so, I need to get on this ASAP.
Note also that “Activity summary” is greyed out and you can’t edit it as long as mailing list mode is selected. But I can deselect mailing list mode, change activity summary settings, and select mailing list mode again. This is a bit weird and seems buggy. Are these mutually exclusive?
Oh - and “Activity Summary” seems to be a duplicate of the first “Email” line - see screenshot.