User blog comment:Omega natsu2/Episode 192: Live on for Her, Review./@comment-24053170-20140726035822/@comment-4829046-20140727132629

1. CS World can always predate the actual keys. The full mechanics are still a mystery so him creating or being present at the creation of the keys is still possible.

2. He obviously has connection due to the Eclipse Gate.

3. We know very little of the timeline of the series prior. It may be possible that either originally the CS were supposed to be used by people like Karin and Angel, as mere tools so the making bonds part isn't really a factor OR that he created the keys during a period where he started caring for life, the former makes more sense though.

So really, the various possible explanations make it quite probable based on info we currently have.