I have existing code using:

gpg --batch --passphrase "<string>" --output "<output file>" --decrypt "<input file>"

(note that my environment for using this feature is secure, so no need to debate merits of using this method)

In 2.3.4 this works as expected and my application can provide the needed password and all works as expected.

In 3.0.0 this string causes gpg.exe to throw an "enter password" prompt.