Dear Joel,
This is partially true. The Global Tropical Moored Array is in OSCAR (~70 moored buoys).
e.g.: https://oscar.wmo.int/surface/#/search/station/stationReportDetails/0-22000-39-5100303
OceanOPS routinely channels metadata for marine observing systems to OSCAR only if the metadata are received from operators according to the standard (www.ocean-ops.org/metadata), and of enough good quality (e.g. with all sensors described)
We are reviewing our metadata standard for moored buoys (and other fixed elements) with the community and we expect to deliver all national moored buoys asap.
Regards,
WMO/OceanOPS Team