Yes I noticed similarity seems harder than congruency as well for many students. The majority of students find this deductive process unrelatable because you can see with your eyes that the shapes are congruent 😂 Why are we trying to prove it.
Random question - I'm a tutor teaching some year 8 kids on geometry proving (triangle congruency, similarity etc). I have learned this a while ago and remembering not enjoying this topic at all because it's a lot of repetition of writing down reasons etc. I was so bad at it but finally caught up...