I think the idea was that early spy satellites would use film rather than digital transmission, so it would be at the very least necessary to potentially grab one's own satellites.

In any case, this exact question was asked here, and the top-rated response indicates that it's unlikely that the design requirement was ever meant to refer to grabbing an uncooperative payload:

https://space.stackexchange.com/questions/41741/was-the-spac...