A probationary period takes the pi**. Did they, or did they not recruit for "experienced pilots"?!
Actually, a probation period is a very good thing for the company. With so many people going through recruitment, there will slip 1 or 2 through the loops who doesn't fit into the environment and makes life hard for everybody, and the probation period gives an opportunity to exchange those very few with some who will fit in better.
Because you are experienced doesn't mean you will fit into every company culture.