He thinks he did and how is that inconsistent
To who's who the group of Luffy and other SNs were just "rats" who needed to be taken care of.
Why would he be so concerned for Drake freeing Law if he thinks so low of them.
Secondly, if the only point was to prove Drake as a snitch why not just say it when all the Tobi Roppo were summoned by Kaido?
Not to mention he relished at the prospect of challenging a calamity.
This could make more sense contextually if they had some beef in the past, but from what we got in the story till this point that reveal does feel a bit weird and inconsistent.