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The place I mentioned allows knife throwing as well. And yes, knife throwing is relevant to feeling confident with a knife.
I don't think it's strange - but I do think it's a place that knife-owning people did meet and greets.
Experience with sharp instruments so as to not cut oneself/leave one's own blood trail out of the house is, IMO, not all that common or usual. This person felt calm with a knife in their hand, while breaking and entering. My personal theory is that they had been in the house before (perhaps even come in when no one was home). But this time they took a fairly large knife, and left no obvious blood evidence of their own behind.
As far as we know. Also, no bloody footprints right outside second floor door, or else the roommate overlooked that in a panic (but we could see for ourselves in the early drone pics and by the evidence markers placed that there were no bloody footprints immediately adjacent to the doors or windows of the house.
I don't think anything is irrelevant at this point in time.