The statement you quoted is absolute, so it can't be applied situationally. Maybe this is just my fault for wording it poorly, but what you're using as a counter example is actually talking about progression arc. Using 2K-style numbers for simplicity. Situation: There are two players, A and B. A staff thinks Player A has Ovl of 79 and a Pot of 83 and Player B Ovl of 70 and Pot of 90. What you're saying is that it's possible that Player B can be the right choice no matter what because they are confident in their ability to develop Player B to reach that Pot. I don't think I'm getting you wrong there, but tell me if I am.
What I'm saying is that if that that staff has to have a sense of how long that both players have to reach their potentials. If A gets to 83 in year two and B gets there in year five or six and then gets to 90 in year eight or nine, it's not clear that even they would want to pick B over A. The arc itself matters. Picking A gets 83-level play for three cheap years. Almost all of the time Player B is at that level, he's being paid like a 83-ovl player and is thus providing less value for his production. Maybe in those four years A was better than B, the GM can put together a contending roster with that extra cap space. Or maybe B walks because they want to get 83-level money but the team isn't in a position to pay that much. If both players walk after their first contract, then the team got way more value for A than B. But even if they make it to two contracts, you can still argue that A was the better pick, because the team had a solid player for longer, and that gave them more flexibility. To complicate matters, even the best staff is only somewhat certain in their progression. B might develop way faster, A might have more potential than believed or one or the other could bust. That discounts the value of the more volatile asset, because present value is worth more than future value.
I'm not saying that chunk of text definitely applies to these players. But point remains that how quickly a guy can develop is definitely important to projecting that player's ceiling, and when it comes to what teams get from their draft picks, picking a whole bunch of players that are only good once they're on their second deals is not viable financially, higher ceiling or no. You need cheap guys producing, unless you have legit MVP candidates on the roster.