It recently came up in a game that some of my spells have some weird material components, so I have been updating my spreadsheet to know what kind of requirements I have. I found one which has to be a mistake, the requirement makes much more sense as a focus.
Now under Magic: Components
A material component consists of one or more physical substances or objects that are annihilated by the spell energies in the casting process. Unless a cost is given for a material component, the cost is negligible. Don't bother to keep track of material components with negligible cost. Assume you have all you need as long as you have your spell component pouch.
Now the offending spell is Swift Girding
Components V, S, M (the armor to be worn)
So according to the RAW I cast the spell and choose some armor which I or others want to wear right now. But the rules for spell components is that the material focus is annihilated. So the armor(s) should never arrive on the target(s). It would make much more sense for this to be a focus.
Was there a mistake when it was copied to the site? Is it presented that way in the book?