Essentially, with this new deal, after equity financing YC will own 7% minus the dilution from the equity round minus dilution from any options pool increase [1]. Previously, after equity financing, YC would own 7% minus the dilution from the equity round minus the dilution from the SAFE round.
While it's true founders are getting a little bump on YC absorbing the dilution from a Series A option pool re-up, in my experience these are typically 5% to maximum 15% increases. Whereas the dilution from post-YC SAFE rounds are typically 15% to maximum 30%. So YC is assuming a potential 5-15% dilution in their ownership while avoiding a 15-30% dilution in their ownership. Translation: YC will own more post-equity financing than they would in the old deal.
This puts a burden on the founders to make up for that increased dilution by raising the post-YC SAFEs at a higher valuation than they otherwise would, which will likely make those raises harder. Alternatively, they can raise their Series A at a higher valuation than they otherwise would to make up for YC's extra ownership, but that will make those raises harder than they otherwise would be. So there is a real dilution downside for founders here.
1: in reality YC will continue to own 7% after the equity round because they'll exercise their pro-rata right during the equity round but that doesn't change the underlying point being made here so will ignore it for simplicity.