It is not just holes. I didn't want to analyze the entire problem in full, but FIY, this is how a concrete sleeper looks like: https://www.google.com/url?sa=i&

It is not just holes. I didn't want to analyze the entire problem in full, but FIY, this is how a concrete sleeper looks like: https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.dayaengineering.com%2Fconcrete-sleepers-blocks-2838240.html&psig=AOvVaw0kn8SM5UBk6C-jGbCF6o3L&ust=1747903778939000&source=images&cd=vfe&opi=89978449&ved=0CBcQjhxqFwoTCPDN_pKXtI0DFQAAAAAdAAAAABAE https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.dayaen... As you can see, the entire shape of the sleeper is adapted to the expected distance between rails. In contrast, a wooden sleeper is just a straight log with no pre-made bumps for rails.