The Cam Jordan extension

Cam would have to agree to reduce his salary for 2024 to vet min. (1.21M) , agree to void the roster bonus, and then file retirement papers after June 1. that would reduce his cap hit this year to about 10.3M for 2024 and about 13.1 in 2025.
Why cant we do that and just pay him cash under the table like Patriots/Brady?