Yes they are OK, but when you mount the mobo in the case don't the metal standoffs give sufficient support? If all you are doing is attaching extra standoffs it is OK but unnecessary.
for both ATX & MATX mobos I use 4 mounting screws (and the standoffs). Nothing more. If you use extra standoffs it is harder to install or later tinker with the mobo if you have to service it.
Thanks for the reply, I see now lol