Just spoke with Samsung support and they advised that DPD are the ones responsible for applying the seal, so it appears they just forgot to do it in this instance
They said I could send it back but I don't know if its worth it, the watch doesn't have any damage or any signs of wear. The screen and rear weren't absolutely 100% dust or residue free but didn't look like fingerprints or use as such, and once wiped off both were pristine.
I know I probably seem ott but when you spend north of £300 on a device you want to make sure it's actually new I guess
Edit: the watch also works fine and connected to my phone no problem. It had about 47% charge which is typical for new stored devices also
Yeah that's probably what I'll do, unless it starts not working properly or something in the next 2 weeks!
They said it's basically not really possible to get a used one from them as they don't have that's option on their site from the warehouse its from, and it's not like the box had a broken seal which would suggest used.