They Could. Signing Bonus does affect your future cap with proration. However look how Ralph operated. if the cap is 200M he is only spending 200M that year. But a cap of 200M the owner could spend DOUBLE that in singing bonuses for and prorate. You can look at the teams that are routinely up against the cap they have very rich owners and within weeks are no longer against the cap. Is a liquidity thing
Because the owner is Willing to convert differed payments (weekly game checks) to a massive one time check. So example when you take 17M in base salary (1M a week for the football season) convert to Bonus. That owner has to cut that 17M check immediately. Multiply that by multiple restructures and signings your owner could cut 100M in checks on Day 1 of UFA.
Unlike the cash to cap of Ralph that would pay but not pay big bonuses to manipulate cap hits. And essentially wait until the shared money comes in (what sets the Cap)
One would be the player asking for the trade. The other is the Team initiating the trade stuff.
That is the distinction, Bills wanted him back at a certain price, Beasley wanted out. Bills obliged.