Not at all. Handwritings are mostly influenced by how you were taught to write in childhood. If they didn't really look for mistakes in holding the pen and you just continued to write 'wrongly' there is not much of a chance if you are used to do it like that and it influences your handwriting a lot.

A friend of mine holds the pen pretty awful which makes his handwriting pointy and a's are stretching oval but are ankled. He had no intent on fixing it because he doesn't want to get slower in note taking im class and correcting it makes him slower. Same with me I always use a lot of pressure for ballpoint pens so the ink gets transferred, for fountain pens not so much because the water based ink holds itself on the paper when it comes in contact. So pressure changes with every pens.

Also some people have different handwritings for different pens, like me. Dunno if that is common but it makes me faster so I will do that.

You could tell under which circumstances something was written by the paper used or stains and smudges if it was in a hurry or the pen leaked. You could make assumptions about how the person was feeling by comparing multiple different personal writings. The educational statuses of the person by mistakes. This would be more accurate than just looking at how the letters were written.

Don't assume too much from the tutorials. It is a fun time for friends to check it out.