There are many kinds of samadhi.Jhana is Right Samadhi.The one taught by Siddharta's teachers were not what The Buddha called Right Samadhi. Right Samadhi which is Jhana can only be achieved if one has Right View.Different kind of samadhi can produce rapture bliss calm.But are not Jhana without Right View.Samatha meditation shouldn't be discouraged as it is a part of the Eight Noble Path.Siddharta remembered The First Jhana when he was meditating under extreme conditions.So he could not have been practicing Right Samadhi Jhana at that point.But he was definitely deep in samadhi.