If the deal is truly increasing over time, then that tells me that the team will do whatever it takes to get under the tax this year. If we were planning on paying the tax this year, we would be front loading the contract with 8% drops each year (to decrease our tax bill down the line, since the tax rate increases as you go further over the tax line). Increasing his salary every year means that we want low salary year 1, and monetarily that makes the most sense if we're trying to avoid the tax.
Edit: Also, if the contract is exactly 4/52 with 8% raises, we can get ~$1 million under the tax line by trading Nader/Yabu/cash/2nds for no salary back (unfortunately, this leaves us about 300k short of resigning Bird to the minimum and staying under the cap)