Just off the press, you can now exclude dumpster from your Public Folders migration from Exchange 2013/2016 to Exchange Online.
Until then the PF dumpster was migrated along with the PF data, resulting in longer public folders migration. Without thinking neither with the potentials issue of data in the dumpster corrupted.
To exclude the dumpster from your PF migration you need to use the new parameter –ExcludeDumpsters when creating the PF migration batch; if you don’t the dumpster will be migrated

New-MigrationBatch -Name PublicFolderMigration -CSVData $bytes -SourceEndpoint $PfEndpoint.Identity -ExcludeDumpsters