From: Klassert
...

quoted

Exporting a userland API (here by /proc) enables a user or a daemon to
choose a strategy according to information the kernel does not
necessarily have, and enables to implement various (possibly complex)
policies.

If we add a user API for the current lookup mechanism, we will stick
with this because we can't change it anymore without breaking userspace.
So I don't want to add one before we finally decided on a long term
lookup mechanism for IPsec.

You could have a user API call to find the list of available mechanisms
as well as one that returns/sets the current one.
Then there is no actual requirement to continue to support any specific one.

	David