Not sure that's correct.
I thought that only applied to clubs who acquire a free agent. Dusty sometimes gets caught up in that category as he was a free agent, but a club re-signing their own player aren't bound by free agency rules.
I could be completely wrong though.
I’m pretty sure you can re-negotiate but the amount stays the same, but can flatten it out over multiple years.
As an example, both Riewoldt and Cotchin re-negotiated their deals in 2018 I believe. They essentially added another year (from 2 to 3) and a bit more $$, but ended up being less per season.
It enabled us to extend the likes of Lambert et al.