No that isn't a conflict and doesn't require a proof post, that just means that most likely someone undercut/overcut the other.
If someone instant sold a bcp at 6125 and someone had a sell offer for 6100 that is a conflict and should be posted.
Also from what I see, conflict proof is used to confirm a lucky buy/sell and/or large stretch in the margin.
In short, if a buy/sell happened, AT THAT MOMENT, that seems impossible, it should be posted. The possibility of them, in your example, cutting one another is very plausible so we shouldn't worry about it.
After searching on this site for 10 minutes or so, I can't find where we address conflicts. I'll ask a rank about it. I might make a small post defining it. I can definitely go into better detail in that.
I didn't feel the need to put this topic in the starter tutorial because I don't want new people having to worry about it when they are first introduced to the chat.