This reading is based on two emendations, originally suggested by Finnur J nsson. The two words vers and unz are extremely similar graphologically, especially in their abbreviated forms. The emendation of frumseyris to frumseyrir can hardly be avoided - otherwise the subject of kom would be missing.
Different readings are, of course, possible.
In stanza 3, Thor starts wading across the ocean. Here he reaches the ocean. This seems to suggest that the order of the stanzas may be incorrect. It may originally have been an epithet of Freyja, cp. Fj lsvinnsm l 38, where Fr is one of Freyja's handmaidens.