Yes, I think there might be a "magic length" for each woman that is just right so as to allow close pubic contact (with indirect clitoral stimulation) and simultaneous stimulation of whatever deep vaginal area (cul-de-sac or AFE) is effective in triggering orgasm, and I suspect for many that length is around 7" or a little more.
The partners I have had who were highly vaginally orgasmic seemed to be such that we had just that perfect fit so that with maximal insertion I could feel that I was exerting a bit of pressure at the end of their vaginal canal. But there were other women who did not seem to find that sensation of deep vaginal pressure stimulating, or were indifferent to it, so I don't think this is something that applies to all women.
The partners I have had who were highly vaginally orgasmic seemed to be such that we had just that perfect fit so that with maximal insertion I could feel that I was exerting a bit of pressure at the end of their vaginal canal. But there were other women who did not seem to find that sensation of deep vaginal pressure stimulating, or were indifferent to it, so I don't think this is something that applies to all women.