Buyer sharing is one piece. The other pieces matter as much.
Start with the terms. A wholesaler puts a property under contract with a seller, then assigns that contract to an end buyer for a fee. The fee is the difference between what you agreed to pay the seller and what the buyer pays you for the right to step into your contract. Deal flow just means the steady stream of possible deals coming at you, how many sellers you're talking to in a month.
A micro-wholesaler network is a group of small operators, often part-time, who pool things so each of them closes more contracts than they would alone. The four things that actually move around are buyers, leads, referrals, and knowledge. Referrals are the underrated one. Say you lock up a rural property with a big lot and none of your 40 buyers wants it. A member whose buyers all want exactly that gets it sold, and you split the assignment fee, often 50/50. You got paid on a deal that would have died.
Knowledge sharing is the fourth. Wholesaling rules vary by state, some states have added registration or disclosure requirements for assignments, and a group that talks about that regularly catches problems an isolated person misses. Confirm anything specific with an attorney licensed where you're working.
On your worry about handing over 40 names: most working groups don't hand over raw lists at all. They pass a deal to the member who has the buyer, and that member keeps the relationship. If the group is asking you to upload your contacts on day one, that's a different arrangement than the one being described to you, and it's fair to ask which one it is before you join.