Why are you using Houck's 2021 AAA numbers? They seem irrelevant. He had a 3.24 ERA in 2019 in AAA. The issue there was that it was mostly out of the pen.
Do you remember why he had previous struggles and why he "suddenly" improved in MLB? When he first got into the organization, they messed with his delivery multiple times instead of just letting him throw the way he always had. Through 2019, he still struggled get LHB out. As an RP, it's not a big deal, but they still hoped he could at least be a spot starter. Thanks to COVID, they left Houck at the Alternate Training Site and intentionally stacked LHB lineups against him to get him to work through it and learn to be a better pitcher. Because of that, he had to learn a splitter. Without that experience, he may not be the MLB pitcher he is today.