That's a good breakdown. I'm a little bit wary of aggregating anything from his 2020 season since it was so short, but he does a good job of contextualizing the small sample sizes. For example, I think you can explain the continued FB-reliance as part of his pitch mix by saying in part that he needed to be able to locate it much better, etc., rather than part of a deliberate strategy. Earlier in the season, it really seemed like our pitchers were only going at about 70-80%. I don't think that totally explains the FB dip, but Keller didn't have the same issues once he came back from his injury.
Overall, I think Keller has to some extent gotten the hyper-observant treatment from some fans, who hang on his every single pitch and want swinging strikes or are worried we'll see a repeat of what happened with Cole. Obviously, this attitude is understandable, but I think based on the eye test of his final starts, there's a lot to remain optimistic about with him. The big question is definitely the combination of injuries and durability, coupled with the related question of FB velo. If those things are all fine, he will instantly look a lot better almost immediately to a lot of people, because the offspeed pitches are already very good. Fastball location and consistency isn't the rarest or worst issue for a young pitcher to have to grapple with, and if anything should be a preliminary sign that Keller's potential has not been put on training wheels by the Searage/Huntington school of pitcher development (I do think, in the end, this strategy is one of the major faults actually worth throwing onto Huntington, not the utterly absurd and false stuff about him preferring to get low ceiling players all the time in trades and whatever other cliches people, including the beat reporters often, are spinning, but I digress...).