This is the changeset for that other area I was thinking of where there is no ramp.
https://www.openstreetmap.org/changeset/145077494
On the north side of the GWB there is a tiny inlet or cove where jetskis can land.  Nothing is ever carried there to my knowledge though it could be. I wouldn't label it as a slipway but maybe another feature?  Certainly a kayak could land there also.