Round 1 folks had the exact same discussion pattern, including the infuriating marketing email. Expect another marketing email in the next two days.
From what I could understand reading the posts from October, R1 had a similar invite distribution, with a small batch on the first day followed by three days of invites (two batches per day). I don't think invites are sent out by concentration. Lots of people got invites on the last day (Friday for R2), but dings also went out on the last day.
If R2 applicant pool is similar to R1 on gmatclub, then we should see around 30-40 invites. I see only two reported so far.
Wscherba
Looks like all invites from today were for USA based consulting or related industries. I believe they invite based on groups. Obviously I do not know the exact parameters in which they segregate apps but. If you are not interested in Consulting and are not from the USA, I would not be concerned at all.
I also reviewed the R1 data and thought they concluded on concentrations. My bad if not. Either way I am Not for profit which is more niche so I will be much more concerned if I start seeing a bunch of those go out.