They are different physical buildings. OVH does not generally claim anything regarding AZ or distance. SBG1, 2, 3, etc is just denoting the building your server

They are different physical buildings. OVH does not generally claim anything regarding AZ or distance. SBG1, 2, 3, etc is just denoting the building your server is in - they are not like AWS style AZ or similar, quite literally just building addresses. I have used them for years and I don't believe they've ever said anything like deploy in both SBG1 and SBG2 for safety or availability, because you don't get that choice. When you provision a machine (eg via API) they tell you "SBG 5 min, LON 5 min, BHS 72h" and you pick SBG and get assigned first-available. There is no "I want to be in SBG4" generally.