Are all interviews with Kanglong rejected on the grounds of full signature?

Yes.

1. Sometimes they tell you that they are full, but they actually mean to reject you. You do not meet their recruitment conditions and you are not suitable for this job, so just say that they are full. It's just an excuse, there's no need to go again.

2. Someone has performed more in line with the requirements. The interviewer thinks that he is better than you and more suitable for this position than you, so he directly rejects the job on the grounds that he has a full signature.