Yes. It's a must for pcc to be stamped by MoFA. This is because on the pcc it self they wrote ( it must be attested by MoFA)
so they leave you with no option but to do it.
Also, just in case you didnt know, MoFA stamps in oman are in arabic only, which is quite useless. I had them stamp some documents that i sent to the canadian medical council to get my ECA and they rejected them as they must be in english or french.
So what i did for my pcc, is i got the MoFA to add another stamp which is Apostille. It costs extra and canada is not part of the apostille international agreement, but i still paid and got it as its in english, and it was accepted by CIC no issues.
Good luck