I wouldn't want Ainge to do this unless he thought Noel was a guy he wanted to sign going forward.
Sure. I just don't think it's as binary as this in most cases. Whether you sign Noel or not can depend on factors such as how he works with the rest of the team, with Stevens, and what other uses you have for the cap space.
[quite]Would be pretty brutal to trade, say Rozier, the 2018 #1 and filler to get Noel, then find out this summer the Bulls kinda liked Rozier.[/quote]
This sort of thinking seems to be too limiting, and would preclude basically any moves. Can also be turned around as "what if we re-sign Noel and then it turns out next trade deadline the Bulls like Noel." If Danny has concrete reason to think that the Bulls have an outsized valuation on Rozier, then fine, hold him back, and offer something else. Applying a blanket fear of the unknown trade filter is problematic however.
It really comes down to how much one likes Noel. I think he's a very good center prospect, with the potential to be top-tier defensively, and average offensively. If you don't think highly of him however, then sure, the option value isn't worth much either.