Now that I think about it, I think this law could also hurt competition even amongst established players, allowing them to squeeze restaurants even harder.
Imagine platforms A, B, and C. Platform A approaches Daisy's Cafe offering an amazing deal on a delivery partnership, as long as the Cafe agrees not to use any other delivery companies. Daisy asks around and hears great things about Platform A, so she says yes – what a win!
Months later, the quality of Platform A starts going way down – food is delivered to the wrong addresses, delivered cold, etc. All of the restaurants in Daisy's area also deliver with Platform A, so the local customers don't use other platforms – she's stuck. If she switches, she'll lose almost all her delivery traffic overnight.
Now imagine if Platform C did delivery for her without an agreement signed. Daisy isn't breaking the agreement with Platform A when customers order through Platform C! She'll still lose business when she stops working with Platform A, but not as much, so it's an easier choice to make.
In this scenario, predatory platforms are more likely to squeeze restaurants if agreements must be signed, because exclusivity can be enforced.
Of course, the simple patch here is to disallow exclusive delivery platform contracts, but I don't see that in this bill.