When the same source (the lore book) takes care to make it very obvious when we have someone with us (by saying that we are not alone and calling out the units of adventurers) then yes this is for me evidence that we are alone. Otherwise why would that example be different and not mention them even though they are there?
@Rope: Tell me then how it would make sense in canon that we have "friends" with us against Titania? We flee from Ranjit (a solo fight with no other adventurers near us) into a country that is protected by the pixies. We do a dungeon (again with the scions) and then make our way through the country and to the different tribes again without any friends. Then everything goes bad fast! Ranjit is there. The others go back to buy us time...and suddenly the WoL who barely even knows anyone on this shards calls in some random 7 other people that arrive there to help us? How would they arrive fast enough? How would we even know them? And why are they gone afterwards instead of flying on the Amaros with us to defeat Ranjit?
How would Innocence make sense? We go at this again only with the scions. How did they get there? Why are they gone afterwards when they could have at least tried to stop Emet? It makes imo no sense to have them there.
Hades is different. This is probably the only in canon fight that is done with 7 other people in shadowbringers. Why? Because we see them being summoned by the exarch in a cutscene before the trial itself (so in story confirmation of it happening) and them being not there at the end also makes sense because I doubt that such a spell can last forever and we did have quite the hard fight. So before they could have helped us more they puffed out of existence. There you have a group fight that makes complete sense and is part of the cutscenes.
With most of the other instances you only have these people come in while in the dungeon/trial/raid and have them disappear afterwards without any reason too.
If the lore writers come out one day and say that this was all done with groups then I have to accept that I saw it wrong. But the lore book does support my view (at least the first one, dont have the second one) and at least the logic makes only much sense if we are alone or with the scions.