I think this post-condition (begin-end while) loop is really similar to that of many other common languages.

For example in both Java and Javascript you have:

do {

     statement(s)

} while (expression);

which will execute the code in the block at least once.

Why in Ruby would that be much of a surprise then?

The only difference is that in Ruby you use "begin-end" (and not "do-end" which can be used to create a block only in some contextes).

Please correct me if I am wrong.