A very likely scenario is that the Phils are out of the playoff race by the trade deadline and have the best starting pitcher available to trade. They could essentially turn $10M (the portion they paid him before being traded) into a nice prospect from a contending team. Imagine what they could get for AJ from a cash-strapped contender if they also agree to pay the rest of his salary for the year.
Rebuilding teams with a large payroll should do more of this, in my opinion. Sign very good veterans to 1 year deals and use them as trade chips at the deadline to infuse more talent into the system.
I see that, but still don't think it's the smartest move.
Suppose Burnett stumbles out of the gate at CBP. The fans crucify him, he's miserable, etc. The team then loses whatever leverage they may have had in trade negotiations and maybe the ideal scenario you posit plays out a little differently. Maybe they have to eat all of the money just to move him. Maybe Amaro wants to keep him, because his loves veterans more than Bowden loved five-tool players.
It's not like that $16MM had to be spent before Opening Day ... save it for a rainy day, Jason Heyward's free agency, or something.