Correct, Pressac wanted it both ways. He frequently wrote in contradiction to himself, but this didn't stop other historians from citing and parroting his opinions. You are highlighting an excellent example of how unserious Holocaust history is.
Pressac repeated this circus act again later in the book.
This “phanthom” document is not “conclusive” proof of the existence of homicidal gas chambers in Krematorium IV. but it helps us to understand and establish how they were planned, built and used.
Contrary to what I said in my article on
“Les Krematorien IV et V de Birkenau” in
“Le Monde Juif”, the three documents cited above [Photos 31, 32 and 33] together with Krermatorium drawings 1678 of 14th August 1942 and 2036 of 11th January 1943 enable us to state that
KREMATORIEN IV AND V WERE DESIGNED AS CRIMINAL INSTRUMENTS, though modifications introduced in the course of their construction and operation made their operating sequence absurd.
https://www.historiography-project.com/ ... tz/447.php
By calling the "operating sequence absurd", Pressac agreed with what Fred Ziffel wrote above about the facility's nonsensical design. Contrary to what you wrote, Pressac believed those absurdities were introduced because of modifications made later, not because of its initial design.
As to what the crematoria were originally designed as, obviously only one theory can be true. If conversion theory is correct -- if KIV and KV were converted from mundane purposes, as you believe -- then how did Pressac get it wrong? And what were the gas chambers originally intended to be? And what would they turn into after, as you imagine, they would be converted a second time?