The simple answer is NOT no but Depends.
For most brands/models mixing and matching is fine but some brands/models use considerbly different IP pressures. Posiden (if I remember correctly) uses a good bit higher IP than most regs so using a different brand octo with a Posiden would cause the octo be be working at a pressure higher than it's design and conversely a Posiden octo on a different brand first stage would be working at a lower than specified IP. It might work but not a good idea.
In general, it's fine to mix and match but a flat statement that any octo can be used with any primary stage is incorrect and possibly dangerous.
For most brands/models mixing and matching is fine but some brands/models use considerbly different IP pressures. Posiden (if I remember correctly) uses a good bit higher IP than most regs so using a different brand octo with a Posiden would cause the octo be be working at a pressure higher than it's design and conversely a Posiden octo on a different brand first stage would be working at a lower than specified IP. It might work but not a good idea.
In general, it's fine to mix and match but a flat statement that any octo can be used with any primary stage is incorrect and possibly dangerous.
