This is right.... just from last year's draft alone, they have Madden, Dylan Smith and Brant Hurter, who, with how they have performed, all look fairly promising. And Garrett Burhenn, who is still in Lakeland and probably shouldn't be based on his performance and experience level.
It is by design, to an extent.. the team sanctioned Road to Detroit podcast had some interview clips with Ryan Garko this week where he said that they aspire to that endless supply of pitching, but I definitely think they are at a point where they can part with one or two of these guys or other prospects (such as Olson or Bergner) if it helps fill these short term positions of need, without it being too much of a burden to the system.
But again, the question then becomes what any of those arms bring back on trade, even if they are paired with a bullpen piece.... fans tend to overrate what they can get in return.