Sleipnir's father was a magic horse, though, and Loki was in the form of a mare when impregnated with Sleipnir. The result of that pairing was half-jotun half-horse.
But Angrboða was jotun just as Loki was, so comparing the pairing of Loki and Angrboða to the pairing of Svaðilfari and Loki is probably not wholly proper.
Especially when we know that in other instances, pairing between Loki and Angrboða produced Hel, who is a goddess, so why would the other pairings between Loki and Angrboða be any different?? Especially since we know that Fenrir, despite his appearance, is fully sapient and capable of intelligent thought and speech.
It's of note that Loki and Angrboða's whole race seems to be capable of shapeshifting. We get many instances in Norse mythology of giants/trolls who take the form of wolves or other creatures (The best being, Síbilja, who was basically a demonic cow). So likely Fenrir is simply a jotun who takes the form of a wolf. Jotun, for the purposes of this thread, seem to count as gods, as Loki, Skadi, and Hel are all reckoned as "gods" commonly.