Whether the Swans pay a negotiated amount or the full year’s salary, I expect the full year’s salary to be included in the Swans’salary cap.
Think of it this way.
Franklin retires with 3 years to go. Swans pay him say 50% of his 3 years’ full salary as a negotiated amount. The negotiated amount is included in the first year’s salary cap. The second year the Swans pay significantly less than the salary cap, allowing the Swans to pay 105% of the cap in year 3. Swans go and get the best free agent in year 3.
If Swans are required to include the full amount in the salary cap (even if they only pay the negotiated amount) then they cannot get the best free agent, etc. as quickly.
EDIT: Or more simply, if the Swans only have to include say half of Tippet’s salary in the 2018 cap, then it can go and get the best free agent next year / retain all its best players (rather than lose one to keep the rest).