I read your post twice and no I don’t think disclosure cost you the job. The time of the interview does seem like it’s on the shorter side, but there could be several reasons for that. You don’t know what the result is until you have it and until then we have a tendency to try to find a reason which frequently we attach to stuttering. Even after we have the result we still try to blame stuttering when there are most likely other reasons. You already described how you don’t want your stuttering to be misinterpreted for nervousness and disclosure is a fantastic way to counter that potential narrative. Stay positive and good luck.