Should Patients Be Informed if a Doctor is Inexperienced in a Certain Procedure?

Research in your doctor is very important.  Some companies like Sculptra require training and certification before the company will even sell the product to the doctor.  Other companies sell their products to anyone.  My suggestion would be to talk to other patients about their experience and also be up front and ask the doctor about their experience with each product you are considering.  Good luck.

Sculptra is not dispensed to doctors without hands on training from a professional trainer. Obviously, the more experience the better your chances of a desirable outcome. Not every doctor has the "eye" required for successfully using Sculptra so it's a good idea to ask to see their Sculptra patient results before you make a physician selection.
Most physicians will perform additional hands-on practicing on people in their inner circle who are not patients first. And some physicians are very dedicated and will take additional trainings before moving into their own patient base.
I train here in the U.S. and also internationally and take extra time to ensure that those under my tutelage understand the concepts

how Sculptra behaves
what it can do and what it can't do
how to plan out the stages of Sculptra "re-sculpting"
facial areas to avoid
patient selection (who can benefit and how)

A successful Sculptra result does require a certain level of artistic concept. From time to time a physician I am training will decide it's simply not a skill he or she wishes to pursue. It is a fact - Sculptra does require more time and more attention to detail and facial balance. There are many fine cosmetic dermatologists and surgeons who are wizards with fillers who simply prefer to stay with those products alone.
Sculptra is not injected the same way as traditional fillers. There are nuances as to injection technique, facial compartment considerations (some areas of the face are not suitable for Sculptra injections and these have to be identified) and even patient selection. Not everyone is a good Sculptra candidate and physicians have to be frank with patients who may not respond adequately due to profound volume loss or skin condition.
As to your question about a physician putting in writing that you are their "first"? I can't comment adequately on that question. From an personal standpoint, I would assume a paying patient is never the "first" patient for any new procedure a physician has undertaken. But I know of no requirement that forces them to divulge that information.