I don't think Houston gets ed on those.
Consider the fork they are in.
1) They can't guarantee Yao is healthy next season. IF he is not, it's blow it up time. Jefferson, expiring fits in beautifully with this. If he is healthy, they need to convince him to stay, which means championship shots; ie talent on the team. That CHI #1, after moving Deng, is likely going to be pretty good. Jefferson would be an expiring that you could trade for actual talent; he's never had Mcgrady's injury or cancer issues.
2) Do you really see better above, from your own post.
Washington: Caron Butler, Mike Miller, Randy Foye
Butler = Jefferson, both are expiring next year, No 1st
Philadelphia: Andre Igoudala, Samuel Dalembert
No expirings, long contracts, it will trap HOU in lux tax for a long time. Dalembert cannot play PF with Yao at C. Iggy >= Jefferson, but no first.
Chicago: Tyrus Thomas, Brad Miller, John Salmons
Miller is an expiring, TT is a lousy prospect at this point, and Salmons < Jefferson. The actual deal proposed in the article is worse, Hinrich +TT = Bad contract + poor prospect.
Knicks: Garbage, garbage, garbage, and Al Harrington
You really like Al Harrington do you? (who's expiring anyway...)
3) What happens if they keep TMAC and let him expire?. Assuming they decide to keep Scola and Lowry (both of whom will want raises) they commit to the qualifying offers, and have $44 million in salary committed. They are second or third tier players in free agency (compare with the nets, knicks, heat, bulls, Clippers, and Kings)...And they have to make the decisions while they don't know if Yao is Healthy.
Moving TMAC for a 1st rounder and put off the salary space until 2011 (when they know about Yao), while getting a usable player in Jefferson, and saving money this season.
Doesn't look like a bad return for a large expiring who's got a bit of a rep as a locker room cancer. I really don't think you're going to get more, and sometimes, it's best just to keep your options open until next season.