Yes. An LSP has to work along with the compiler, or it has to become an alternative compiler.

For example, from the article "Why LSP?" [1]

"It is known that compilers are complicated, and a language server is a compiler and then some."

[1]: https://matklad.github.io//2022/04/25/why-lsp.html

It's moving in that direction, but far from all are based on their compiler still.