Variable replacement for query optimisation is tricky

sparql-var-replace.md

One query example:

select * {
  ?s1 <urn:p> ?o1
  optional { ?s1 <urn:q> ?t1 }
  ?s2 <urn:r> ?o2
  optional { 
    ?s2 <urn:s> ?t2
    filter(?t1 = ?t2)
  }
}

Assuming no literals in the graph, can one take advantage of the equality condition and rewrite it to

select * {
  ?s1 <urn:p> ?o1
  optional { ?s1 <urn:q> ?t1 }
  ?s2 <urn:r> ?o2
  optional { 
    ?s2 <urn:s> ?t1
    bind(?t1 as ?t2)
  }
}

? If yes, what's the argument? If not, why not?