The comments and code below say that a weight of one is being used as a weight of zero. If a project is mature, or eventually becomes mature, a weight of one may in fact be a useful weighting, and the project owners will become very confused when they are unable to receive funds with this weighting.
There is 1 instance of this issue:
https://github.com/jbx-protocol/juice-contracts-v2-code4rena/blob/828bf2f3e719873daa08081cfa0d0a6deaa5ace5/contracts/JBFundingCycleStore.sol#L467-L471
