Confusion Between Simple & Compound Tenses with Restrictive NE..QUE

Using restrictive ne … que to express only with simple tenses (French Negations)

--> In this lesson on Simple Tenses with Restrictive Ne..Que it states this (quoting below) - 

ATTENTION:
 
You CANNOT place que in front of the verb, so you CANNOT express He only eats pasta on Saturdays. 

Therefore, since que cannot be placed in front of/ just before the MAIN verb in Simple Tenses, I can only say -

     -- Il ne mange que des pâtes le Samedi. [He eats only pasta on Saturday.] (i.e. restricting pasta or Saturday, as per the lesson)

 

 

--> But as per this lesson on Compound Tenses with Restrictive Ne...Que, I can say? - 

    -- Il n'a que mangé des pâtes le Samedi. [He only ate pasta on Saturday.]

So, now the rule changed and I CAN place que just before the MAIN verb and after the AUX. verb??

And thus, that rule mentioned under 'ATTENTION' heading in Simple Tenses is NOT true for Compound Tenses ??  (Technically, I CANNOT say "He only eats pasta" in French, but I CAN say "He only ate pasta" in French?)