Problems with DEFSYSTEM-DEPENDS-ON

The usage of DEFSYSTEM-DEPENDS-ON to specify dependencies that will be satisfied by QL:QUICKLOAD no longer seems to be working in asdf-3.3.1.

It used to be the case that to use the [PROVE testing framework][1], it was sufficient to place a

… :defsystem-depends-on (:prove-asdf) …

clause in the secondary system to be tested, and then upon a QL:QUICKLOAD of this system, the dependency on PROVE was then resolved via a network download from Quicklisp.

[1]: https://github.com/fukamachi/prove

I believe this was working with asdf-3.2, but testing that assumption is a little hard as asdf-3.3 refuses to degrade itself with a downgrade, and all my systems are running asdf-3.3.

Maybe something in Quicklisp changed as well?