Hello Aspirant,
Hope you are doing well.

Yes, it is correct. One of the professors at my university completed her residency in ophthalmology before switching to ear, nose, and throat surgery for her fellowship. She was not doing it at the same time as anything else. She completed a postgraduate degree in ophthalmology, then retook the test and completed a postgraduate degree in otolaryngology. After that, she went back to working in otolaryngology-head and neck surgery.

Because of the high level of competition in PG entrance exams, many students choose a branch that is not their first choice and then study for their preferred branch. It is not a good idea to get up and leave your seat. What good is it when you can not acquire your preferred branch the following time?
Hope you got the answer to your question. Incase of any queries, feel free to question. Have a great day!