Pumps for Deioned Water

Recently came across a Food Mfr with HACCP ,using pumps of Cast Iron Construction whereas piping system is in Stainless Steel
Is this right or engineer simply dont realise ?

If the pump is for pumping raw water to Deionised System , not too bad but still , we are giving unnecessary extra load to the filters in the system, with rust  ,extra

And if , the pump is for treated or Deionised Water ,then you are contaminating the water again

As the system builder has installed the cast iron pump , the user just follow the same replacment
without giving a thought

We do highlight , that  stainless steel pump should be used
What he said ? Expensive

And this happened despite Inspector from relevant food department audited the plant