OP is actually right on this subject matter. Just because a girl touches you on the arm/back doesn’t automatically signal that she likes likes you. It could mean she is either warming up to you, or is down right messing around.
If you have a chance, read the The Definitive Book of Body Language, the book explains in great detail that it is super important that you read the entire human body as a whole. That means you must observe the person’s facial expressions, the way how they move their feet, how they behave around others, etc. We humans are really complicated creatures. Whatever comes out from our mouths will not always correlate with how we really feels about an/a individual/group/situation.
Edit: grammar correction on second to last line of this comment.
I would read The Definitive Guide to Body Language and practice giving the correct 'signals' so you leave as good of an impression as possible. If there are two candidates of equal technical prowess, the one who would be a better fit for company culture (aka more likable) will generally get the position. It's a way to approach the interview from an analytical mindset focusing on the soft skills.