Extension with multiple “pdf” (or any) based formats?

[mcanouil]

Currently, a Quarto extension can define multiple formats as long as they are different:

contributes:
  format:
    html:
      # html-specifc
    pdf:
      # pdf-specifc

But, how to define twice (or more) "pdf" formats?
For example:

contributes:
  format:
    pdf:
      # letter format
    pdf:
      # thesis format

---

I do not think it's possible with the current API,
It would need to explicitly define the format name instead of it being define by the base format and the name of the extension.

contributes:
  format:
    letter-pdf:
      base-format: pdf
      # letter format
    thesis-pdf:
      base-format: pdf
      # thesis format

Where in a Quarto document it could be used as below:

format: thesis-pdf

Am I missing something?