It's not hindsight for many.
This sounds to me like an argument that the current Twins coaching staff needs upgrading. Is that your point? The Twins don't have the staff to get the most out of players?
Not to mention, there's no guarantee Pressly needed any "unlocking." As Spycake and others have pointed out, Pressly was already really good, and getting better, when dealt.
I'm not trying to be that judgmental of the Twins coaching staff. I think a player's developmental progression is highly path dependent, and that the dynamics of when/how coaches work with a player aren't necessarily recreate-able. I don't blame the Twins for every single played that has found success in other organizations. Sure, I think you can make judgments of the organization's ability based on the broad pattern of players, but certainly not on any one specific player. Using Pressly as an example, it is fairly well known that the Astros came to him after the trade and presented data for how to change his pitch mix. The Twins could have presented the exact same information, but Pressly has a much longer track record with the Twins organization, and there might not be the same buy-in, especially since he was already pitching as well as he ever had in his career. The Astros, by virtue of being a fresh voice and having explicitly sought Pressly out, could approach these changes in a very different way than the Twins could.
And yes, Pressly was pitching well prior to the trade, but you need to put a lot of weight on his last 10 appearances with the Twins if you think you could predict his Astros level of success based on his Twins performance. Now, don't get me wrong, I think he was a solid bet to be above-average going forward; I did not predict "top 5 reliever in baseball". As an interesting juxtaposition, the Pirates acquired Keone Kela at the same deadline. While not a perfect analogy to Pressly, he was also a young, very good reliever with team control remaining. He is currently on the 60-day IL with a shoulder issue. Teams only have so much control over preventing injuries. Are we having this conversation if Pressly was the one that ended up injured? Reliever performance is historically quite volatile, I don't hold it against the Twins FO that they thought it was a sell-high moment for Pressly.
Going back to the small sample size, what is everyone's prediction for Duffey going forward? His last ten appearances compared to Pressly's prior to the trade:
Pressly: 10.0 IP, 0.90 ERA, 33.3 K%, 7.1 BB%, 1.10 WHIP
Duffey: 13.0 IP, 0.69 ERA, 32.1 K%, 7.1 BB%, 1.08 WHIP
I've been extremely optimistic about Duffey for weeks now, but I'm not ready to anoint him a top-10 relief pitcher going forward. But at least superficially, there are a lot of similarities between Duffey this year and Pressly's 2018.