There are two strings containing this phrase:
"The globally unique identifier of the item. E. g. the feed item GUID in the case of a syndication feed. May be unique."
"The external URL of the item. E. g. the feed item URL in the case of a syndication feed. May be unique."
In the case of the latter it is obvious, that it should be "must be unique". Nevertheless, may be unique is useless information, so I think all should be "must be unique".

Comments

MegaChriz’s picture

MegaChriz CreditAttribution: MegaChriz commented
Issue summary: View changes
Status: Active » Closed (works as designed)

"may be unique" refers to the fact that the target can be used as an unique target. Feeds doesn't force you to use "GUID" and "URL" as unique target. Feeds doesn't even force you that the values imported into these targets are unique. So "may be unique" is correct here.

I agree though that in most cases you would only use these targets just to have an unique target. But even in that case "must be unique" is still technically incorrect.