Hiya, small problem, and maybe visual only – there is this. option for site-admins:

“Site Admin Only: update email subscription settings for ALL members to the default: Daily Digest. Warning: this is not reversible so use with caution. Make it so!”

When I do this, all with most recent versions of WordPress, BuddyPress and the plugin, nothing changes. I haven’t been able to verify whether the change actually happened or not; I think so…