Tim, both words matter. As you mention, the "handshake" part implies a degree of welcoming or greeting. I don't gather from the quote or from Ross' work on the ground that he sought to open you with a ball buster. The "firm" part, to me, implies a certain degree of accountability to the player. It's a greeting, and as you call out, an opportunity to swing with some freedom and see how the ball is flying and rolling. But it's not some wussified hole that hands out participation medals either.
In other words, there's a balance. "Firm handshake" calls out that balance - it's a hole where you're given an opportunity to get comfortable and build some confidence for the rest of the round, but you'll need to deliver sturdy swings. "Gentle handshake" removes that balance, which is why it's not an expression anyone has ever used except when misquoting.
I find that when discussing architecture, certainly on this site, there tends to be a drift toward emphasizing the "gentle" and "handshake" sides of the equation, and away from the "firm" side. For example, You'll find that people rave about "half-par" holes a lot more often when they're a half-par easy... we love a lot more 470 yard par 5s than 470 yard par 4s, even though both are par 4.5 holes. We laud 270 yard par 4s, but the only 230 yard par 3 anybody around here will speak of glowingly is 16 at Cypress.
Ross' work, at least in my experiences with it, is awfully consistent about maintaining the balance implied by a "firm handshake." The Ross openers I've played tend to be broad-shouldered holes of at least medium length that encourage full swings with some room to play. There aren't any forced carries or real lost ball opportunities I can think of on the ones I've played. But they're also challenging holes where par is well-earned. They give you a fair opportunity to find a good start, but not without solid play.
And I'm with him - those are my favorite types of opening holes, and when I think of the best openers I've played, a host of Ross holes pop to mind along with a few others that I think he'd probably have appreciated.