The processor capabilities vector is not the API you want.

What you want is an API to ask the ssl library about characteristics of algorithm implementations it will be using.

Those are not the same thing.

If we want to expose processor capabilities as a library function it should not be done in the ssl module.  That information belongs in the platform module.  And doing so should not require a third party library such as OpenSSL.  Querying capabilities is a very simple instruction and every platform architecture specific C macros to do it.