I think they are solving two different problems at the same time. One is the order of elements in a single operation (SELECT then FROM then WHERE etc), and the second is the actual pipelining which replaces the need for nested queries.

It does seem like the former could be solved by just loosening up the grammar to allow you to specify things in any order. Eg this seems perfectly unambiguous:

  from customer
  group by c_custkey
  select c_custkey, count(*) as count_of_customers