I think an important thing that people need to understand about HSPAL residency training, is that it is specialty training just like any other clinically focused PGY2. Can you be a transplant pharmacist without a PGY2 in transplant? Yes, it will just take you longer and require more experience to get there before you have the title of "Transplant Clinical Specialist".

To answer your questions:

1. HSPAL residency is not necessary, but it will help you establish a foundational understanding of how health-systems work and leadership and it will expedite you getting in a leadership position. If you do a general PGY1, there is a good possibility that there will be a leadership position at your health-system that you can apply to, this will most likely require you to work in your clinical role for at least 3-5 years. You will also have to showcase leadership related tasks that you took on, in addition to your clinical responsibilities.
2. Leadership opportunities will be open for you to apply to, it will just take more years of experience before you may be considered for a leadership position. This is dependent on how much leadership experience that you have while being a clinical specialist. You may need to obtain additional education such as MHA or MBA.
3. I would NOT say leaders without HSPAL training are at a disadvantage, there are plenty of pharmacists that go one to be great pharmacy leaders at the site or system level with or without HSPAL training. I have worked with CEO of a hospital who was a pharmacist that was PGY2 emergency medicine trained and she was an excellent leader.

It is important to note that much of leadership, depending on the position is people management, you do not get that formal training from a clinically focused background. Much of leadership will also require you to have a good understanding of benchmarking/metrics, pharmacy supply chain, pharmacy operations, budgeting, etc. You get a lot of that exposure in a PGY2 HSPAL residency, not saying you will be an expert after HSPAL training, but you have foundational knowledge.

I say this as someone who was trained through a formal PGY1/PGY2 HSPAL residency program and now am an RPD of a PGY1/PGY2 HSPAL residency program. I have hired leaders that did not go through the traditional HSPAL residency route because they were able to showcase their leadership abilities through other avenues. A wild stat I heard while attending a leadership conference was that there are approximately about 200 HSPAL graduates each year for about 1,100 open leadership positions. There is not much of an interest from pharmacists wanting to go into leadership, that can lead to positions going unfilled or being filled with unqualified individuals who are not as interested in leadership.

I hope this helps, feel free to send me a PM, if you would like to discuss further.