The first kind of touching the scene may remind him of some past scenes, perhaps a smile or a little gesture of yours touched a chord in his heart, perhaps a memory you left him, or a coincidence with someone. Is it a confession? Not necessarily.
Maybe when he recovered from his emotional state, "I miss you" was just a sentence. If he can continue to express this sentence afterwards, it will be his confession.
The second is caused by the other person's personality. Seeing you say "I miss you", your appearance makes him see you and express his good feelings, depending on how well you know him.
The third is social language, which quickly brings your closer with joking and relaxed language. Let's listen to it.
In short, to "miss you" means to be close, whether it is confession or oral words.