I tend to think we over-state how easily a man's honor was considered "engaged" at the time. There is every indication in Austen's novels that courtships did not always lead to engagements, and it wasn't a scandal when they didn't. In the example of Wentworth, who we know found himself in an uncomfortable situation, he had been paying Louisa attentions for more than just a few weeks, and within a small circle of acquaintances who did everything together. They had spent way more time together than Jane and Bingley. In Bingley's case, I am not sure why Mr. Bennet should have been demanding Bingley show up, as if he had compromised Jane, or done something scandalous. He just danced with her and talked to her. And he wasn't, at that point, planning on leaving, except for just a few days. So maybe if Mr. Bennet had realized that Bingley was about to skip town he might have had reason to speak with him, but forcing a proposal after only six weeks of acquaintance, because he danced with her a couple of times and talked to her through supper? That seems rather extreme to me.
I'm on the side that Bingley was young and overly modest, and simply believed too much in Darcy's judgement. Based on Darcy's testimony he was prepared to hold out against every argument about her family or circumstances, until he was convinced that Jane didn't love him. We could spend time discussing why that would be such a deterrent--why he wasn't willing to come back and keep trying, but the common idea that Bingley broke up with Jane because he feared his sister's anger is just not true.
