Yes, and while that may be an advantage for actual use of the language in practice, I think it's a disadvantage for learning the concepts behind OOP and logic programming.
Prolog forces you to solve your problem with logic programming. You cannot take the easy way out and solve it (wholly or partially) in some other way that you already know. Likewise, Smalltalk forces you to solve the problem with OOP. Haskell forces you to deal with pure functions and lazy evaluation. APL forces you to solve the problem with vector operations.
Some of the approaches and solutions may be clumsy and worse than what you can do with a mix or some other programming paradigm. But I thought the point of the exercise was to learn the different programming paradigms, and in that context I prefer programming languages that do not offer alternative ways of solving the problem. I prefer a more restrictive approach and lisp is anything but restrictive (CLOS, kanren, etc).
Also I find that a different surface syntax helps me context switch to a different programming paradigm. For example, when I see s-expressions my mind switches to scheme and thinks accordingly, and that would be a distraction to me if I wanted to program imperatively, for example. When I see Prolog, I have a hard time thinking in terms of OOP. Maybe that's just me.
The reason for suggesting Smalltalk first was that it's farther away from Haskell than Prolog (Prolog clauses can appear similar to functional programming). Switching to Prolog after Smalltalk is another big jump. I like big jumps. They help me switch context. The OP may be different, I don't know.