In-protocol bids will be less valuable than out-of-protocol bids.
A reason for this is that cancels are not possible for in-protocol bids.
Cancels are still needed, as proposers will have different deadlines.
This exposes originators to adverse selection risks, so they'll bid less.
Defaulting to trustless bids therefore limits proposer choice to (1) a subset of bids (2) that is in expectation less valuable.
This will typically affect unsophisticated proposers running on default settings.