I don't follow why your rephrasing is SIA-specific.

Here I'm not arguing for SIA in particular, just against the position that you should only update when your observations completely exclude a world (i.e. 'non-indexical' updating, as in Radford Neal's 'full non-indexical conditioning' for instance). If we just talk about the evidence of existence, before you know anything else about yourself (if that's possible) SSA also probably says you shouldn't update, though it does say you should update on other such evidence in the way I'm arguing, so doesn't have the same problems as this non-indexical position.

I'm addressing this instead of the usual question because I want to settle the debate.