I feel that an introductory meetup CAN be a great thing. However, I can't see where doing so is going to be of particular benefit to all relationships, in all circumstances, under every condition.
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When we had our open triad, Tracy started dationg Scott. Meeting him briefly at a party, he left no particular impression on me. She insisted on bringing him over one evening so the four of us could watch movies (no, NOT porn

) & hang out & chat & "get to know each other," though I warned her this probably wasn't a good idea.
Sure enough, on their way back to his place, he groused about how I was "too friendly" & therefore "fake."

Tracy told me this & I just shrugged, said that kinda made him sound like an immature, egocentric dick.

Her choice, her life, y'know?
Tracy didn't want to leave it there, though. Her solution?
Another movie night.
I thought it went rather well. I didn't ice Scott, I was polite as I'd be to any non-threatening stranger, & I simply avoided addressing him directly because that's what had bothered him.
And naturally he subsequently complained about me being "rude" & "arrogant."

A fewmonths later, Tracy suddenly discovered that Scott was an immature, egocentric dick

& dumped him.
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Even if a meetup is useful or positive, it might not be particularly dramatic.
Anne was interested in dating Larry (married to Heidi). Larry assured Anne that he had an open relationship with Heidi (no DADT, but no need to constantly "check in" for every flirtation or dinner date).
I had no reason to doubt veracity, but suggested it might not be a terrible idea for Anne to confirm it herself with Heidi. Anne thought it'd be fun to make a short evening of it, & arranged to meet up at a nice bistro.
Heidi & I found each other socially likable, but there was no particular attraction there. We had a good time, Heidi & I exchanged phone numbers in case of doubts or questions (sort of a "thing" in our household), & I think that's the last time we ever met. (Anne & Larry had some fun together, but it didn't pan out as a longterm thing.)
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it is much more difficult for men to meet women in an open/poly relationship than it is for women who are in open relationships.
IME, no.
I'm rather fussy about getting intimate with someone new, yet I had less difficulty "keeping my dance card full" than either of my (beautiful, intelligent, personable, bisexual) partners.
And while "meeting new men" isn't much trouble at all for openly nonmonogamous women, IME most of those guys are useless: bride-shopping, or harem-building, or idle fantasizers, or "dick pix" wankers.
Meanwhile, the women who chatted me up had mostly at least attempted to wrap their heads around my lifestyle. They flirted with me with some idea of what they might be getting into, rather than getting stuck in how they might "fix" me.