NHL/NHLPA agreed back in 2020 to cap escrow at 6%, along with only bumping up the cap ceiling 1 mill per season until the escrow debt is paid off. NHL is willing to move on the cap ceiling as the debt is nearly paid off, but only if the players move on the escrow to cover any potential deviation from the 50/50 split. Problem is the players hate the escrow with a passion(irrationally so, since they get it back if the revenue projections hit), and refuse to make any changes to the fixed rate negotiated on despite the fact that it'll go back to being calculated based on the salary cap next year anyways(probably back up to around 10%).
So it's not really about Bettman demanding concessions, rather he's saying they want to resume regular cap operation ahead of schedule and the NHLPA has to agree to it(which includes raising the cap and normalizing escrow), and the NHLPA is adamantly against it because they want that fixed escrow rate.