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)
![Big Grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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