The jhānas, and 4 jhānas, are more than just samatha. If you want to learn what the Buddha meant by jhāna in the EBT, then you have to do some research. Vism., Abhidhamma, the later period of Theravada, redefined jhāna, vedana, kāya, into something entirely different. Unfortunately, the survivors write the history books, so the vast majority of Theravadins have a very distorted version of Dhamma interpreted through later Theravada filters.
Here’s a good thread from a while back. You can see how Bhante G. started off with a view just like you, and 30 years later, after studying the EBT carefully, his understanding of jhāna was entirely different.