Was just sent an advertisement for a Job opportunity doing just GYN and no OB. There are places that exist.
Fellowships are usually geared towards that specialty, hence "subspecialty".
Some of the MIS trained fellows still cover OB calls. There are a few that I know who are deem "Director of Minimally invasive gyn" but still have to cover calls.
Doing JUST gynecology may not cover your overhead for private practice if that's what you are aiming for, unless you are going into an existing practice that has a lot of patients and surgery.
i.e. If I perform an annual gyn-well women exam for a patient, I may get $75-125 pending location
If I do a delivery, may be $1000 pending insurance and location, and each visits can be billed separately for $50-100 pending insurance and location.
If I perform a hysterectomy, $600-800 pending insurance and location.
The above numbers are approximate for NYC & mostly Medicaid and Medicaid HMO.
Some of the hospitals right now are only looking for laborist, which covers only labor & delivery. Then they hire physicians who will only do gyn and gyn surgeries. This is a cost effective model because people who cover OB, usually have higher malpractice insurance.
i.e. In NYC, if you cover OB, your malpractice is about $170,000. if you cover only GYN major, then its about $90,000.
So to answer your question in short,
It is HARD to do just GYN if you are opening a new practice.
It should NOT be too difficult if you join an existing practice looking for a GYN surgeon only.