To my knowledge it's true what you say. Backups without "copy only" flag can mess up your backup chain:
“Copy Only backup is an independent backup and it does not break the chain of database backup LSN (Log Sequence Number). In another word, it does not disturb the original backup workflow, but just create a copy of the original database independently.”
More can be read in a post of Pinal Dave on SQL Authority or for example the doc pages of VEAAM.
So, back to VSS, according to the documentation the Copy-only must be called up on explicitly:
"The requestor can set the backup type as a copy-only backup by setting the VSS_BACKUP_TYPE option as VSS_BT_COPY with the call"
In my demonstration I didn't called up on it explicitly, the only thing "supported" by Hobocopy is: