This is not a contradiction.
Since SHACL-SPARQL processors also support SHACL Core, SHACL-SHACL performs checks that are relevant to them as well.
> On Apr 23, 2017, at 6:43 PM, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
>
>>
>> Note that SHACL-SHACL implements constraints that need to be checked for every
>> shapes graph - whether it is was designed to be used with a SHACL Core
>> processor or with a SHACL-SPARQL processor.
>
> This does not align with wording in the SHACL document:
> "The following shapes graph is intended to enforce many of the syntactic
> constraints related to SHACL Core in this specification."