Here's the letter. I don't think I agree. I'd argue there's much less ambiguous language they could have used then.

As you are aware, the supply of JYNNEOS available for distribution through the end of this year is estimated to only be sufficient to immunize half of the individuals at highest risk for monkeypox. In the absence of an adequate supply, we have evaluated the use of alternative vaccines and potential ways to maximize the number of individuals immunized with the available vaccine supply. Use of alternative vaccines was determined to be either impractical or inadvisable at this time.

More specifically, ACAM2000 may not be appropriate now for a potentially immunocompromised population. The local and systemic toxicities of this vaccine may not be considered to be acceptable for the prevention of monkeypox. Consideration was also given to delaying second vaccine doses by 3 to 6 months. However, following careful review of the available animal data with JYNNEOS, and acknowledging the absence of data applicable to this situation, this option was determined to be inadvisable, particularly because it might both be insufficiently protective while at the same time providing individuals with a false sense of reassurance that they were protected against monkeypox when the actual level of protection would be unknown and quite possibly inadequate.

As they did later on when speaking of doses of JYNNEOS.

Yes, this dose is appropriate for individuals who are taking PrEP or PEP. The Fact Sheet for Healthcare Providers Administering Vaccine notes that Immunocompromised persons, including those receiving immunosuppressive therapy, may have a diminished immune response to JYNNEOS.

That, and well, we are all pretty much immunocompromised at this point. Turns out multiple infections of a virus that attacks endothelial cells isn't a good idea.