Firstly; it seems as though I misremembered what I read; breakfast reservations can be made "up to 90 days in advance"
"Lunch and dinner reservations can be made up to 180 days in advance, and are strongly recommended for all meals, especially dinner. Breakfast reservations can be made up to 90 days in advance."
"Breakfast is finally coming to Be Our Guest Restaurant!
Start your day the French way—with espresso, café au lait and assorted pastries, from croissant and
pain au chocolat to our French croissant doughnut! You can insure a
bon jour with a fluffy omelet, breakfast sandwich or scrambled eggs, all perfectly prepared to soothe the hungriest beast.
Quick-service breakfast is available from 8:00 AM to 10:00 AM, and reservations are recommended.
Dining plans are accepted for breakfast."
https://disneyworld.disney.go.com/dining/magic-kingdom/be-our-guest-restaurant/
Maybe I'm missing something but I don't see any indication of a testing (though I don't know what it said before) currently in place.