the percentages shown in sos slot are actually meaningless and if they're referenced in game at all it's probably for how they handled the slot mechanic to separate between different pokemon. So it's only a 1% chance, not a 1% chance to make a further 1% call.So Salamence has a 1% chance of being called of a SOS slot that has a 1% chance of being picked, all from a Pokemon that has a 1% chance of appearing in the wild.
You have a one in a million chance of getting an SOS Salamence (as your first call. It's 1/10000 if we disregard that).
Otherwise you'd never see Bagon SOS call anyone, since you'll note the other Bagons are only listed with the 1% encounter as well.
Even in the original SM you'd be hard pressed to do this. You still dont have the adreniline orbs so you can't kick start Bagon's calls. You don't have false swipe to guarantee easily getting it into the red range. Your resources for lasting through this are pretty limited in general and actually fighting a Salamence can be a pain due to its base stats. Also have to worry about tracking when Bagon gets low on PP. And if you fail to catch the thing you have to search out another 1% bagon.Iirc the atrociosly low chance of actually getting SOSd salamences was one of the reasons for which it was ranked that low in the VR for ingame USUM runs.
On top of the fact that you don't have the intimidate orbs yet at that point, and actually need to backtrack once acquired.