It’s an SA, except too many places started using SA for sales roles, so now we have the FDE role which… is starting to get polluted by sales, too.

Based on what I first heard it described as, yeah, I think so.

In most places I've worked SAs are generally just connecting existing pieces of a system together to meet a customers needs. They may write code, but it's often just glue to connect two bits of the system together or transform some data or something like that. They're not really contributing to the underlying product, they're just using the product and some custom code to meet a specific customer's needs.

An FDE is supposed to be closer to a regular software engineer on a product or platform team in that their goal is to solve a specific customers problem, but they're supposed to be more focused on the big picture and using their learnings to build a better product. They're still using existing systems to solve problems and writing plenty of glue code, but they're also supposed to have the leeway to contribute to the underlying product to make it better for all customers.

The simplest example I can think of would be something like a customer saying something like they need a way to convert a bunch of their data to a CSV and then send that to a certain email address every Friday. A more traditional SA mindset may be to write a Python script that runs on a cron that connects to that customers DB pulls the data, converts it to CSV, and then emails that specific email address. Even if the SA knows that's not the best way to do it, it's the tools they've been given to work work. A FDE should have the leeway and skills to go talk to a PM and their engineering team and just build an in product, self serve tool to do that (assuming everyone is aligned that that is good for the product).

Again though, what I've heard is that most FDEs at most companies are just SAs by another name.

I think it is. I work for a (relatively) small company. I naturally grew from project engineer to senior/lead/sme (including pioneering tech _for my industry_) to SA. I had also stuck with my company for many years, so I have the industry connections and got to be known as a heavy hitter. That trust relationship with the customers mixed with technical know how = sales and consulting.

Again, because of the size of my company I can make my role fluid (including a good way), but call it what you will I engineer, I sell, I consult.

It's looking like the answer is no. They're the same within the bounds of ordinary differences in the role between companies.