I dont believe the statement by OPO is correct either. You should challenge them to provide a source.
Its always best to go to the definitive source. In this case, the
Panama Canal Authority. The only related announcement Ive found on their site says nothing about closure to small craft, only restrictions on small craft relating to COVID-19. Link below:
https://www.pancanal.com/common/maritime/advisories/2020/ADV-14-2020.pdf