AngloPaleo, the timings are to solidify a proper circadian rhythm (cortisol-based) to help circumvent the leptin pathway for those who aren't currently able to use it.
Kruse is a strong proponent of IF *after* you are leptin sensitive. If you are leptin resistant, you may be shocked at the effects the 50g breakfast may have on you. If not, no need to worry about it; carry on as you were!
For me, the BAB enabled me to get to the point where, without even trying, I was no longer hungry for lunch, and have regularly been eating only twice a day for five months. No hunger. Lots of IF benefits. Lots of weight loss. I've IF'd breakfast-breakfast once with no trouble at all. Once I get my hormone stuff fully up to speed, I'll be doing that more often.